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	$174.58	11.510%	$194.6742	$194.67	$194.65	$194.70
Purchase #2	$233.89	6.540%	$249.1864	$249.19	$249.20	$249.20
Purchase #3	$67.89	13.425%	$77.0042	$77.00	$77.00	$77.00
Purchase #4	$139.82	8.695%	$151.9773	$151.98	$152.00	$152.00
Purchase #5	$83.72	6.192%	$88.9039	$88.90	$88.90	$88.90
Purchase #6	$71.98	8.445%	$78.0587	$78.06	$78.05	$78.10
Purchase #7	$245.68	4.663%	$257.1361	$257.14	$257.15	$257.10
7 purchase totals =	$1,017.56		$1,096.9408	$1,096.94	$1,096.95	$1,097.00