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	$118.97	10.450%	$131.4024	$131.40	$131.40	$131.40
Purchase #2	$41.43	12.512%	$46.6137	$46.61	$46.60	$46.60
Purchase #3	$141.91	10.117%	$156.267	$156.27	$156.25	$156.30
Purchase #4	$79.45	12.529%	$89.4043	$89.40	$89.40	$89.40
Purchase #5	$99.40	6.278%	$105.6403	$105.64	$105.65	$105.60
Purchase #6	$143.61	11.252%	$159.769	$159.77	$159.75	$159.80
Purchase #7	$16.35	9.350%	$17.8787	$17.88	$17.90	$17.90
7 purchase totals =	$641.12		$706.9754	$706.97	$706.95	$707.00