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	$174.32	10.798%	$193.1431	$193.14	$193.15	$193.10
Purchase #2	$81.81	4.113%	$85.1748	$85.17	$85.15	$85.20
Purchase #3	$56.32	11.826%	$62.9804	$62.98	$63.00	$63.00
Purchase #4	$110.43	13.262%	$125.0752	$125.08	$125.10	$125.10
Purchase #5	$181.83	9.741%	$199.5421	$199.54	$199.55	$199.50
Purchase #6	$17.59	7.816%	$18.9648	$18.96	$18.95	$19.00
Purchase #7	$81.61	9.627%	$89.4666	$89.47	$89.45	$89.50
7 purchase totals =	$703.91		$774.3470	$774.34	$774.35	$774.40