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	$101.48	4.417%	$105.9624	$105.96	$105.95	$106.00
Purchase #2	$239.62	6.180%	$254.4285	$254.43	$254.45	$254.40
Purchase #3	$207.71	8.780%	$225.9469	$225.95	$225.95	$225.90
Purchase #4	$105.41	4.631%	$110.2915	$110.29	$110.30	$110.30
Purchase #5	$142.33	12.785%	$160.5269	$160.53	$160.55	$160.50
Purchase #6	$169.33	7.282%	$181.6606	$181.66	$181.65	$181.70
Purchase #7	$59.34	4.692%	$62.1242	$62.12	$62.10	$62.10
7 purchase totals =	$1,025.22		$1,100.9410	$1,100.94	$1,100.95	$1,100.90