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	$188.92	10.405%	$208.5771	$208.58	$208.60	$208.60
Purchase #2	$74.67	5.106%	$78.4827	$78.48	$78.50	$78.50
Purchase #3	$74.66	13.148%	$84.4763	$84.48	$84.50	$84.50
Purchase #4	$245.41	10.436%	$271.021	$271.02	$271.00	$271.00
Purchase #5	$43.89	5.563%	$46.3316	$46.33	$46.35	$46.30
Purchase #6	$143.54	6.274%	$152.5457	$152.55	$152.55	$152.50
Purchase #7	$154.72	4.185%	$161.195	$161.20	$161.20	$161.20
7 purchase totals =	$925.81		$1,002.6294	$1,002.64	$1,002.70	$1,002.60