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	$99.44	11.856%	$111.2296	$111.23	$111.25	$111.20
Purchase #2	$106.92	13.483%	$121.336	$121.34	$121.35	$121.30
Purchase #3	$179.64	9.148%	$196.0735	$196.07	$196.05	$196.10
Purchase #4	$148.72	12.804%	$167.7621	$167.76	$167.75	$167.80
Purchase #5	$108.68	9.461%	$118.9622	$118.96	$118.95	$119.00
Purchase #6	$213.78	5.413%	$225.3519	$225.35	$225.35	$225.40
Purchase #7	$138.93	5.328%	$146.3322	$146.33	$146.35	$146.30
7 purchase totals =	$996.11		$1,087.0475	$1,087.04	$1,087.05	$1,087.10