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	$171.42	9.771%	$188.1694	$188.17	$188.15	$188.20
Purchase #2	$41.56	7.394%	$44.6329	$44.63	$44.65	$44.60
Purchase #3	$52.75	4.782%	$55.2725	$55.27	$55.25	$55.30
Purchase #4	$209.28	11.605%	$233.5669	$233.57	$233.55	$233.60
Purchase #5	$75.88	13.207%	$85.9015	$85.90	$85.90	$85.90
Purchase #6	$174.43	12.447%	$196.1413	$196.14	$196.15	$196.10
Purchase #7	$135.83	4.226%	$141.5702	$141.57	$141.55	$141.60
7 purchase totals =	$861.15		$945.2547	$945.25	$945.20	$945.30