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	$190.76	8.258%	$206.513	$206.51	$206.50	$206.50
Purchase #2	$9.81	10.474%	$10.8375	$10.84	$10.85	$10.80
Purchase #3	$227.64	10.142%	$250.7272	$250.73	$250.75	$250.70
Purchase #4	$162.48	8.845%	$176.8514	$176.85	$176.85	$176.90
Purchase #5	$107.50	12.658%	$121.1074	$121.11	$121.10	$121.10
Purchase #6	$222.81	10.537%	$246.2875	$246.29	$246.30	$246.30
Purchase #7	$90.72	9.425%	$99.2704	$99.27	$99.25	$99.30
7 purchase totals =	$1,011.72		$1,111.5944	$1,111.60	$1,111.60	$1,111.60