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	$175.64	9.262%	$191.9078	$191.91	$191.90	$191.90
Purchase #2	$55.62	7.833%	$59.9767	$59.98	$60.00	$60.00
Purchase #3	$223.79	4.452%	$233.7531	$233.75	$233.75	$233.80
Purchase #4	$156.28	7.300%	$167.6884	$167.69	$167.70	$167.70
Purchase #5	$11.46	10.299%	$12.6403	$12.64	$12.65	$12.60
Purchase #6	$238.65	7.404%	$256.3196	$256.32	$256.30	$256.30
Purchase #7	$83.36	11.230%	$92.7213	$92.72	$92.70	$92.70
7 purchase totals =	$944.80		$1,015.0072	$1,015.01	$1,015.00	$1,015.00