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	$99.86	12.201%	$112.0439	$112.04	$112.05	$112.00
Purchase #2	$147.55	11.227%	$164.1154	$164.12	$164.10	$164.10
Purchase #3	$127.99	7.231%	$137.245	$137.25	$137.25	$137.20
Purchase #4	$76.61	8.753%	$83.3157	$83.32	$83.30	$83.30
Purchase #5	$245.71	7.147%	$263.2709	$263.27	$263.25	$263.30
Purchase #6	$58.54	13.281%	$66.3147	$66.31	$66.30	$66.30
Purchase #7	$164.72	12.701%	$185.6411	$185.64	$185.65	$185.60
7 purchase totals =	$920.98		$1,011.9467	$1,011.95	$1,011.90	$1,011.80