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	$78.82	6.109%	$83.6351	$83.64	$83.65	$83.60
Purchase #2	$155.29	12.442%	$174.6112	$174.61	$174.60	$174.60
Purchase #3	$55.97	5.235%	$58.9	$58.90	$58.90	$58.90
Purchase #4	$212.29	9.847%	$233.1942	$233.19	$233.20	$233.20
Purchase #5	$85.98	12.265%	$96.5254	$96.53	$96.55	$96.50
Purchase #6	$54.99	8.694%	$59.7708	$59.77	$59.75	$59.80
Purchase #7	$235.76	9.392%	$257.9026	$257.90	$257.90	$257.90
7 purchase totals =	$879.10		$964.5393	$964.54	$964.55	$964.50