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	$174.50	4.688%	$182.6806	$182.68	$182.70	$182.70
Purchase #2	$123.52	13.429%	$140.1075	$140.11	$140.10	$140.10
Purchase #3	$141.55	8.657%	$153.804	$153.80	$153.80	$153.80
Purchase #4	$84.89	12.260%	$95.2975	$95.30	$95.30	$95.30
Purchase #5	$232.89	12.243%	$261.4027	$261.40	$261.40	$261.40
Purchase #6	$53.67	10.786%	$59.4588	$59.46	$59.45	$59.50
Purchase #7	$148.76	12.699%	$167.651	$167.65	$167.65	$167.70
7 purchase totals =	$959.78		$1,060.4021	$1,060.40	$1,060.40	$1,060.50