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	$81.25	13.277%	$92.0376	$92.04	$92.05	$92.00
Purchase #2	$236.48	11.483%	$263.635	$263.64	$263.65	$263.60
Purchase #3	$140.34	8.600%	$152.4092	$152.41	$152.40	$152.40
Purchase #4	$88.52	4.478%	$92.4839	$92.48	$92.50	$92.50
Purchase #5	$174.46	9.557%	$191.1331	$191.13	$191.15	$191.10
Purchase #6	$59.62	11.109%	$66.2432	$66.24	$66.25	$66.20
Purchase #7	$163.73	5.445%	$172.6451	$172.65	$172.65	$172.60
7 purchase totals =	$944.40		$1,030.5871	$1,030.59	$1,030.65	$1,030.40