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	$54.91	11.799%	$61.3888	$61.39	$61.40	$61.40
Purchase #2	$234.57	7.654%	$252.524	$252.52	$252.50	$252.50
Purchase #3	$182.32	7.143%	$195.3431	$195.34	$195.35	$195.30
Purchase #4	$41.30	3.196%	$42.6199	$42.62	$42.60	$42.60
Purchase #5	$92.74	11.166%	$103.0953	$103.10	$103.10	$103.10
Purchase #6	$178.64	9.300%	$195.2535	$195.25	$195.25	$195.30
Purchase #7	$234.29	6.353%	$249.1744	$249.17	$249.15	$249.20
7 purchase totals =	$1,018.77		$1,099.3990	$1,099.39	$1,099.35	$1,099.40