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	$98.59	8.500%	$106.9702	$106.97	$106.95	$107.00
Purchase #2	$128.69	12.609%	$144.9165	$144.92	$144.90	$144.90
Purchase #3	$155.64	8.686%	$169.1589	$169.16	$169.15	$169.20
Purchase #4	$33.29	10.479%	$36.7785	$36.78	$36.80	$36.80
Purchase #5	$109.97	3.307%	$113.6067	$113.61	$113.60	$113.60
Purchase #6	$155.88	6.141%	$165.4526	$165.45	$165.45	$165.50
Purchase #7	$78.67	13.692%	$89.4415	$89.44	$89.45	$89.40
7 purchase totals =	$760.73		$826.3249	$826.33	$826.30	$826.40