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	$250.37	7.256%	$268.5368	$268.54	$268.55	$268.50
Purchase #2	$83.92	5.458%	$88.5004	$88.50	$88.50	$88.50
Purchase #3	$74.55	9.675%	$81.7627	$81.76	$81.75	$81.80
Purchase #4	$235.64	8.737%	$256.2279	$256.23	$256.25	$256.20
Purchase #5	$209.78	11.213%	$233.3026	$233.30	$233.30	$233.30
Purchase #6	$145.30	11.855%	$162.5253	$162.53	$162.55	$162.50
Purchase #7	$11.83	3.802%	$12.2798	$12.28	$12.30	$12.30
7 purchase totals =	$1,011.39		$1,103.1355	$1,103.14	$1,103.20	$1,103.10