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	$230.29	4.563%	$240.7981	$240.80	$240.80	$240.80
Purchase #2	$104.38	7.389%	$112.0926	$112.09	$112.10	$112.10
Purchase #3	$219.44	10.511%	$242.5053	$242.51	$242.50	$242.50
Purchase #4	$46.89	11.601%	$52.3297	$52.33	$52.35	$52.30
Purchase #5	$116.41	11.306%	$129.5713	$129.57	$129.55	$129.60
Purchase #6	$139.52	3.612%	$144.5595	$144.56	$144.55	$144.60
Purchase #7	$91.86	12.721%	$103.5455	$103.55	$103.55	$103.50
7 purchase totals =	$948.79		$1,025.4020	$1,025.41	$1,025.40	$1,025.40