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	$104.44	4.634%	$109.2797	$109.28	$109.30	$109.30
Purchase #2	$98.55	7.400%	$105.8427	$105.84	$105.85	$105.80
Purchase #3	$85.25	3.676%	$88.3838	$88.38	$88.40	$88.40
Purchase #4	$72.42	5.719%	$76.5617	$76.56	$76.55	$76.60
Purchase #5	$158.38	12.872%	$178.7667	$178.77	$178.75	$178.80
Purchase #6	$193.80	3.276%	$200.1489	$200.15	$200.15	$200.10
Purchase #7	$221.52	13.717%	$251.9059	$251.91	$251.90	$251.90
7 purchase totals =	$934.36		$1,010.8894	$1,010.89	$1,010.90	$1,010.90