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	$196.26	4.210%	$204.5225	$204.52	$204.50	$204.50
Purchase #2	$125.40	6.329%	$133.3366	$133.34	$133.35	$133.30
Purchase #3	$101.67	10.141%	$111.9804	$111.98	$112.00	$112.00
Purchase #4	$234.51	3.332%	$242.3239	$242.32	$242.30	$242.30
Purchase #5	$114.85	7.399%	$123.3478	$123.35	$123.35	$123.30
Purchase #6	$90.95	7.749%	$97.9977	$98.00	$98.00	$98.00
Purchase #7	$152.92	4.573%	$159.913	$159.91	$159.90	$159.90
7 purchase totals =	$1,016.56		$1,073.4219	$1,073.42	$1,073.40	$1,073.30