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	$108.54	11.378%	$120.8897	$120.89	$120.90	$120.90
Purchase #2	$83.45	7.803%	$89.9616	$89.96	$89.95	$90.00
Purchase #3	$219.84	7.379%	$236.062	$236.06	$236.05	$236.10
Purchase #4	$103.44	7.543%	$111.2425	$111.24	$111.25	$111.20
Purchase #5	$208.87	5.536%	$220.433	$220.43	$220.45	$220.40
Purchase #6	$221.62	7.152%	$237.4703	$237.47	$237.45	$237.50
Purchase #7	$115.60	13.780%	$131.5297	$131.53	$131.55	$131.50
7 purchase totals =	$1,061.36		$1,147.5888	$1,147.58	$1,147.60	$1,147.60