Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$212.91	8.450%	$230.9009	$230.90	$230.90	$230.90
Purchase #2	$112.39	12.559%	$126.5051	$126.51	$126.50	$126.50
Purchase #3	$244.88	8.170%	$264.8867	$264.89	$264.90	$264.90
Purchase #4	$130.78	11.520%	$145.8459	$145.85	$145.85	$145.80
Purchase #5	$174.47	7.734%	$187.9635	$187.96	$187.95	$188.00
Purchase #6	$225.73	10.116%	$248.5648	$248.56	$248.55	$248.60
Purchase #7	$214.35	11.392%	$238.7688	$238.77	$238.75	$238.80
7 purchase totals =	$1,315.51		$1,443.4357	$1,443.44	$1,443.40	$1,443.50