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	$11.74	4.535%	$12.2724	$12.27	$12.25	$12.30
Purchase #2	$209.74	3.378%	$216.825	$216.83	$216.85	$216.80
Purchase #3	$190.42	12.583%	$214.3805	$214.38	$214.40	$214.40
Purchase #4	$181.56	4.324%	$189.4107	$189.41	$189.40	$189.40
Purchase #5	$112.39	7.513%	$120.8339	$120.83	$120.85	$120.80
Purchase #6	$148.48	12.139%	$166.504	$166.50	$166.50	$166.50
Purchase #7	$128.59	11.373%	$143.2145	$143.21	$143.20	$143.20
7 purchase totals =	$982.92		$1,063.4410	$1,063.43	$1,063.45	$1,063.40