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	$183.37	4.129%	$190.9413	$190.94	$190.95	$190.90
Purchase #2	$100.64	11.200%	$111.9117	$111.91	$111.90	$111.90
Purchase #3	$19.33	4.457%	$20.1915	$20.19	$20.20	$20.20
Purchase #4	$219.99	10.602%	$243.3133	$243.31	$243.30	$243.30
Purchase #5	$184.64	13.225%	$209.0586	$209.06	$209.05	$209.10
Purchase #6	$155.38	11.151%	$172.7064	$172.71	$172.70	$172.70
Purchase #7	$167.43	5.835%	$177.1995	$177.20	$177.20	$177.20
7 purchase totals =	$1,030.78		$1,125.3223	$1,125.32	$1,125.30	$1,125.30