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	$78.69	9.641%	$86.2765	$86.28	$86.30	$86.30
Purchase #2	$53.33	10.737%	$59.056	$59.06	$59.05	$59.10
Purchase #3	$123.49	11.150%	$137.2591	$137.26	$137.25	$137.30
Purchase #4	$48.66	3.462%	$50.3446	$50.34	$50.35	$50.30
Purchase #5	$209.42	10.622%	$231.6646	$231.66	$231.65	$231.70
Purchase #6	$189.80	12.437%	$213.4054	$213.41	$213.40	$213.40
Purchase #7	$139.55	4.693%	$146.0991	$146.10	$146.10	$146.10
7 purchase totals =	$842.94		$924.1053	$924.11	$924.10	$924.20