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	$200.37	4.417%	$209.2203	$209.22	$209.20	$209.20
Purchase #2	$194.43	13.712%	$221.0902	$221.09	$221.10	$221.10
Purchase #3	$147.33	8.764%	$160.242	$160.24	$160.25	$160.20
Purchase #4	$165.71	10.820%	$183.6398	$183.64	$183.65	$183.60
Purchase #5	$125.72	13.281%	$142.4169	$142.42	$142.40	$142.40
Purchase #6	$160.59	3.469%	$166.1609	$166.16	$166.15	$166.20
Purchase #7	$20.35	4.344%	$21.234	$21.23	$21.25	$21.20
7 purchase totals =	$1,014.50		$1,104.0041	$1,104.00	$1,104.00	$1,103.90