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	$88.69	13.599%	$100.751	$100.75	$100.75	$100.80
Purchase #2	$73.58	12.303%	$82.6325	$82.63	$82.65	$82.60
Purchase #3	$146.89	12.438%	$165.1602	$165.16	$165.15	$165.20
Purchase #4	$51.26	3.697%	$53.1551	$53.16	$53.15	$53.20
Purchase #5	$243.84	13.826%	$277.5533	$277.55	$277.55	$277.60
Purchase #6	$145.87	6.136%	$154.8206	$154.82	$154.80	$154.80
Purchase #7	$209.84	10.610%	$232.104	$232.10	$232.10	$232.10
7 purchase totals =	$959.97		$1,066.1767	$1,066.17	$1,066.15	$1,066.30