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	$110.70	13.409%	$125.5438	$125.54	$125.55	$125.50
Purchase #2	$207.25	7.342%	$222.4663	$222.47	$222.45	$222.50
Purchase #3	$129.45	9.784%	$142.1154	$142.12	$142.10	$142.10
Purchase #4	$164.77	4.111%	$171.5437	$171.54	$171.55	$171.50
Purchase #5	$220.43	5.757%	$233.1202	$233.12	$233.10	$233.10
Purchase #6	$191.58	9.131%	$209.0732	$209.07	$209.05	$209.10
Purchase #7	$53.49	3.828%	$55.5376	$55.54	$55.55	$55.50
7 purchase totals =	$1,077.67		$1,159.4002	$1,159.40	$1,159.35	$1,159.30