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	$180.36	5.330%	$189.9732	$189.97	$189.95	$190.00
Purchase #2	$142.83	12.334%	$160.4467	$160.45	$160.45	$160.40
Purchase #3	$193.46	12.641%	$217.9153	$217.92	$217.90	$217.90
Purchase #4	$188.41	4.217%	$196.3552	$196.36	$196.35	$196.40
Purchase #5	$247.57	11.143%	$275.1567	$275.16	$275.15	$275.20
Purchase #6	$199.82	8.619%	$217.0425	$217.04	$217.05	$217.00
Purchase #7	$103.51	5.578%	$109.2838	$109.28	$109.30	$109.30
7 purchase totals =	$1,255.96		$1,366.1734	$1,366.18	$1,366.15	$1,366.20