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	$88.34	8.653%	$95.9841	$95.98	$96.00	$96.00
Purchase #2	$221.60	10.386%	$244.6154	$244.62	$244.60	$244.60
Purchase #3	$73.72	11.700%	$82.3452	$82.35	$82.35	$82.30
Purchase #4	$40.61	5.593%	$42.8813	$42.88	$42.90	$42.90
Purchase #5	$203.96	9.599%	$223.5381	$223.54	$223.55	$223.50
Purchase #6	$207.38	13.424%	$235.2187	$235.22	$235.20	$235.20
Purchase #7	$158.39	8.120%	$171.2513	$171.25	$171.25	$171.30
7 purchase totals =	$994.00		$1,095.8341	$1,095.84	$1,095.85	$1,095.80