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	$188.82	13.434%	$214.1861	$214.19	$214.20	$214.20
Purchase #2	$159.62	4.462%	$166.7422	$166.74	$166.75	$166.70
Purchase #3	$98.67	8.293%	$106.8527	$106.85	$106.85	$106.90
Purchase #4	$103.85	9.409%	$113.6212	$113.62	$113.60	$113.60
Purchase #5	$219.56	6.135%	$233.03	$233.03	$233.05	$233.00
Purchase #6	$79.38	12.543%	$89.3366	$89.34	$89.35	$89.30
Purchase #7	$123.52	12.753%	$139.2725	$139.27	$139.25	$139.30
7 purchase totals =	$973.42		$1,063.0413	$1,063.04	$1,063.05	$1,063.00