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	$64.27	11.355%	$71.5679	$71.57	$71.55	$71.60
Purchase #2	$55.67	3.607%	$57.678	$57.68	$57.70	$57.70
Purchase #3	$9.71	13.744%	$11.0445	$11.04	$11.05	$11.00
Purchase #4	$61.92	8.437%	$67.1442	$67.14	$67.15	$67.10
Purchase #5	$53.33	4.741%	$55.8584	$55.86	$55.85	$55.90
Purchase #6	$110.38	8.388%	$119.6387	$119.64	$119.65	$119.60
Purchase #7	$34.43	3.253%	$35.55	$35.55	$35.55	$35.60
7 purchase totals =	$389.71		$418.4817	$418.48	$418.50	$418.50