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	$184.93	13.499%	$209.8937	$209.89	$209.90	$209.90
Purchase #2	$47.83	9.729%	$52.4834	$52.48	$52.50	$52.50
Purchase #3	$178.77	9.589%	$195.9123	$195.91	$195.90	$195.90
Purchase #4	$206.56	13.208%	$233.8424	$233.84	$233.85	$233.80
Purchase #5	$19.59	8.131%	$21.1829	$21.18	$21.20	$21.20
Purchase #6	$155.38	8.213%	$168.1414	$168.14	$168.15	$168.10
Purchase #7	$153.27	12.703%	$172.7399	$172.74	$172.75	$172.70
7 purchase totals =	$946.33		$1,054.1960	$1,054.18	$1,054.25	$1,054.10