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	$33.85	7.152%	$36.271	$36.27	$36.25	$36.30
Purchase #2	$55.66	7.832%	$60.0193	$60.02	$60.00	$60.00
Purchase #3	$91.89	9.187%	$100.3319	$100.33	$100.35	$100.30
Purchase #4	$237.31	11.507%	$264.6173	$264.62	$264.60	$264.60
Purchase #5	$42.56	8.302%	$46.0933	$46.09	$46.10	$46.10
Purchase #6	$37.26	3.556%	$38.585	$38.59	$38.60	$38.60
Purchase #7	$176.56	7.448%	$189.7102	$189.71	$189.70	$189.70
7 purchase totals =	$675.09		$735.6280	$735.63	$735.60	$735.60