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	$114.67	9.377%	$125.4226	$125.42	$125.40	$125.40
Purchase #2	$228.30	7.552%	$245.5412	$245.54	$245.55	$245.50
Purchase #3	$70.27	4.263%	$73.2656	$73.27	$73.25	$73.30
Purchase #4	$59.50	5.171%	$62.5767	$62.58	$62.60	$62.60
Purchase #5	$167.46	3.169%	$172.7668	$172.77	$172.75	$172.80
Purchase #6	$31.29	5.692%	$33.071	$33.07	$33.05	$33.10
Purchase #7	$170.34	10.109%	$187.5597	$187.56	$187.55	$187.60
7 purchase totals =	$841.83		$900.2036	$900.21	$900.15	$900.30