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	$186.88	9.390%	$204.428	$204.43	$204.45	$204.40
Purchase #2	$137.57	6.691%	$146.7748	$146.77	$146.75	$146.80
Purchase #3	$229.33	6.150%	$243.4338	$243.43	$243.45	$243.40
Purchase #4	$118.78	10.753%	$131.5524	$131.55	$131.55	$131.60
Purchase #5	$142.83	7.619%	$153.7122	$153.71	$153.70	$153.70
Purchase #6	$63.84	4.506%	$66.7166	$66.72	$66.70	$66.70
Purchase #7	$196.92	11.541%	$219.6465	$219.65	$219.65	$219.60
7 purchase totals =	$1,076.15		$1,166.2643	$1,166.26	$1,166.25	$1,166.20