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	$83.33	11.869%	$93.2204	$93.22	$93.20	$93.20
Purchase #2	$100.64	11.787%	$112.5024	$112.50	$112.50	$112.50
Purchase #3	$94.38	12.466%	$106.1454	$106.15	$106.15	$106.10
Purchase #4	$150.56	9.442%	$164.7759	$164.78	$164.80	$164.80
Purchase #5	$154.90	11.614%	$172.8901	$172.89	$172.90	$172.90
Purchase #6	$33.32	12.623%	$37.526	$37.53	$37.55	$37.50
Purchase #7	$29.52	10.338%	$32.5718	$32.57	$32.55	$32.60
7 purchase totals =	$646.65		$719.6320	$719.64	$719.65	$719.60