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	$99.75	7.127%	$106.8592	$106.86	$106.85	$106.90
Purchase #2	$130.52	13.648%	$148.3334	$148.33	$148.35	$148.30
Purchase #3	$42.88	5.229%	$45.1222	$45.12	$45.10	$45.10
Purchase #4	$62.78	3.361%	$64.89	$64.89	$64.90	$64.90
Purchase #5	$92.39	11.219%	$102.7552	$102.76	$102.75	$102.80
Purchase #6	$56.34	13.834%	$64.1341	$64.13	$64.15	$64.10
Purchase #7	$226.99	11.202%	$252.4174	$252.42	$252.40	$252.40
7 purchase totals =	$711.65		$784.5115	$784.51	$784.50	$784.50