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	$219.30	5.472%	$231.3001	$231.30	$231.30	$231.30
Purchase #2	$81.54	9.592%	$89.3613	$89.36	$89.35	$89.40
Purchase #3	$166.87	3.178%	$172.1731	$172.17	$172.15	$172.20
Purchase #4	$212.27	8.166%	$229.604	$229.60	$229.60	$229.60
Purchase #5	$38.91	9.607%	$42.6481	$42.65	$42.65	$42.60
Purchase #6	$182.35	10.733%	$201.9216	$201.92	$201.90	$201.90
Purchase #7	$200.72	4.538%	$209.8287	$209.83	$209.85	$209.80
7 purchase totals =	$1,101.96		$1,176.8369	$1,176.83	$1,176.80	$1,176.80