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	$126.76	5.420%	$133.6304	$133.63	$133.65	$133.60
Purchase #2	$172.47	10.530%	$190.6311	$190.63	$190.65	$190.60
Purchase #3	$23.92	13.530%	$27.1564	$27.16	$27.15	$27.20
Purchase #4	$174.83	12.240%	$196.2292	$196.23	$196.25	$196.20
Purchase #5	$47.73	6.818%	$50.9842	$50.98	$51.00	$51.00
Purchase #6	$234.52	4.814%	$245.8098	$245.81	$245.80	$245.80
Purchase #7	$222.85	6.714%	$237.8121	$237.81	$237.80	$237.80
7 purchase totals =	$1,003.08		$1,082.2532	$1,082.25	$1,082.30	$1,082.20