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	$195.63	5.558%	$206.5031	$206.50	$206.50	$206.50
Purchase #2	$120.46	9.221%	$131.5676	$131.57	$131.55	$131.60
Purchase #3	$190.52	10.201%	$209.9549	$209.95	$209.95	$210.00
Purchase #4	$165.34	4.252%	$172.3703	$172.37	$172.35	$172.40
Purchase #5	$112.39	4.440%	$117.3801	$117.38	$117.40	$117.40
Purchase #6	$67.62	6.305%	$71.8834	$71.88	$71.90	$71.90
Purchase #7	$147.88	9.332%	$161.6802	$161.68	$161.70	$161.70
7 purchase totals =	$999.84		$1,071.3396	$1,071.33	$1,071.35	$1,071.50