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	$83.84	6.635%	$89.4028	$89.40	$89.40	$89.40
Purchase #2	$152.31	6.284%	$161.8812	$161.88	$161.90	$161.90
Purchase #3	$170.54	11.299%	$189.8093	$189.81	$189.80	$189.80
Purchase #4	$114.99	13.329%	$130.317	$130.32	$130.30	$130.30
Purchase #5	$176.56	5.779%	$186.7634	$186.76	$186.75	$186.80
Purchase #6	$141.56	13.830%	$161.1377	$161.14	$161.15	$161.10
Purchase #7	$112.94	12.628%	$127.2021	$127.20	$127.20	$127.20
7 purchase totals =	$952.74		$1,046.5135	$1,046.51	$1,046.50	$1,046.50