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	$93.62	4.252%	$97.6007	$97.60	$97.60	$97.60
Purchase #2	$179.76	9.198%	$196.2943	$196.29	$196.30	$196.30
Purchase #3	$208.90	4.674%	$218.664	$218.66	$218.65	$218.70
Purchase #4	$77.49	3.352%	$80.0875	$80.09	$80.10	$80.10
Purchase #5	$140.88	13.663%	$160.1284	$160.13	$160.15	$160.10
Purchase #6	$121.69	4.728%	$127.4435	$127.44	$127.45	$127.40
Purchase #7	$18.92	9.488%	$20.7151	$20.72	$20.70	$20.70
7 purchase totals =	$841.26		$900.9335	$900.93	$900.95	$900.90