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	$235.56	11.309%	$262.1995	$262.20	$262.20	$262.20
Purchase #2	$82.54	8.782%	$89.7887	$89.79	$89.80	$89.80
Purchase #3	$159.33	13.800%	$181.3175	$181.32	$181.30	$181.30
Purchase #4	$174.36	6.285%	$185.3185	$185.32	$185.30	$185.30
Purchase #5	$63.98	10.528%	$70.7158	$70.72	$70.70	$70.70
Purchase #6	$94.64	9.508%	$103.6384	$103.64	$103.65	$103.60
Purchase #7	$56.84	7.750%	$61.2451	$61.25	$61.25	$61.20
7 purchase totals =	$867.25		$954.2235	$954.24	$954.20	$954.10