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	$148.33	11.827%	$165.873	$165.87	$165.85	$165.90
Purchase #2	$114.46	4.299%	$119.3806	$119.38	$119.40	$119.40
Purchase #3	$175.55	9.211%	$191.7199	$191.72	$191.70	$191.70
Purchase #4	$203.57	12.267%	$228.5419	$228.54	$228.55	$228.50
Purchase #5	$5.47	11.655%	$6.1075	$6.11	$6.10	$6.10
Purchase #6	$52.79	13.598%	$59.9684	$59.97	$59.95	$60.00
Purchase #7	$99.57	4.166%	$103.7181	$103.72	$103.70	$103.70
7 purchase totals =	$799.74		$875.3094	$875.31	$875.25	$875.30