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	$168.70	9.119%	$184.0838	$184.08	$184.10	$184.10
Purchase #2	$97.31	3.748%	$100.9572	$100.96	$100.95	$101.00
Purchase #3	$238.39	10.783%	$264.0956	$264.10	$264.10	$264.10
Purchase #4	$107.60	10.220%	$118.5967	$118.60	$118.60	$118.60
Purchase #5	$225.89	12.660%	$254.4877	$254.49	$254.50	$254.50
Purchase #6	$127.98	7.646%	$137.7654	$137.77	$137.75	$137.80
Purchase #7	$98.89	13.647%	$112.3855	$112.39	$112.40	$112.40
7 purchase totals =	$1,064.76		$1,172.3719	$1,172.39	$1,172.40	$1,172.50