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	$232.78	7.788%	$250.9089	$250.91	$250.90	$250.90
Purchase #2	$148.83	11.318%	$165.6746	$165.67	$165.65	$165.70
Purchase #3	$164.62	4.666%	$172.3012	$172.30	$172.30	$172.30
Purchase #4	$141.25	8.596%	$153.3919	$153.39	$153.40	$153.40
Purchase #5	$67.94	4.839%	$71.2276	$71.23	$71.25	$71.20
Purchase #6	$37.93	7.371%	$40.7258	$40.73	$40.75	$40.70
Purchase #7	$181.86	4.545%	$190.1255	$190.13	$190.15	$190.10
7 purchase totals =	$975.21		$1,044.3555	$1,044.36	$1,044.40	$1,044.30