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	$161.59	11.608%	$180.3474	$180.35	$180.35	$180.30
Purchase #2	$148.82	11.756%	$166.3153	$166.32	$166.30	$166.30
Purchase #3	$100.29	4.333%	$104.6356	$104.64	$104.65	$104.60
Purchase #4	$161.41	12.717%	$181.9365	$181.94	$181.95	$181.90
Purchase #5	$89.84	8.159%	$97.17	$97.17	$97.15	$97.20
Purchase #6	$80.81	12.117%	$90.6017	$90.60	$90.60	$90.60
Purchase #7	$21.27	13.374%	$24.1146	$24.11	$24.10	$24.10
7 purchase totals =	$764.03		$845.1211	$845.13	$845.10	$845.00