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	$62.51	13.120%	$70.7113	$70.71	$70.70	$70.70
Purchase #2	$124.28	12.227%	$139.4757	$139.48	$139.50	$139.50
Purchase #3	$218.82	9.782%	$240.225	$240.23	$240.25	$240.20
Purchase #4	$159.83	4.117%	$166.4102	$166.41	$166.40	$166.40
Purchase #5	$111.36	6.403%	$118.4904	$118.49	$118.50	$118.50
Purchase #6	$101.54	7.868%	$109.5292	$109.53	$109.55	$109.50
Purchase #7	$193.51	13.323%	$219.2913	$219.29	$219.30	$219.30
7 purchase totals =	$971.85		$1,064.1331	$1,064.14	$1,064.20	$1,064.10