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	$146.31	12.571%	$164.7026	$164.70	$164.70	$164.70
Purchase #2	$24.75	5.626%	$26.1424	$26.14	$26.15	$26.10
Purchase #3	$119.67	3.433%	$123.7783	$123.78	$123.80	$123.80
Purchase #4	$249.32	7.483%	$267.9766	$267.98	$268.00	$268.00
Purchase #5	$240.31	11.843%	$268.7699	$268.77	$268.75	$268.80
Purchase #6	$185.33	8.144%	$200.4233	$200.42	$200.40	$200.40
Purchase #7	$89.49	11.452%	$99.7384	$99.74	$99.75	$99.70
7 purchase totals =	$1,055.18		$1,151.5315	$1,151.53	$1,151.55	$1,151.50