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	$181.28	4.173%	$188.8448	$188.84	$188.85	$188.80
Purchase #2	$231.61	5.573%	$244.5176	$244.52	$244.50	$244.50
Purchase #3	$65.48	7.694%	$70.518	$70.52	$70.50	$70.50
Purchase #4	$64.78	6.612%	$69.0633	$69.06	$69.05	$69.10
Purchase #5	$104.47	13.853%	$118.9422	$118.94	$118.95	$118.90
Purchase #6	$140.53	3.712%	$145.7465	$145.75	$145.75	$145.70
Purchase #7	$232.74	4.697%	$243.6718	$243.67	$243.65	$243.70
7 purchase totals =	$1,020.89		$1,081.3042	$1,081.30	$1,081.25	$1,081.20