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	$236.66	9.466%	$259.0622	$259.06	$259.05	$259.10
Purchase #2	$38.46	7.443%	$41.3226	$41.32	$41.30	$41.30
Purchase #3	$35.60	13.411%	$40.3743	$40.37	$40.35	$40.40
Purchase #4	$243.77	13.148%	$275.8209	$275.82	$275.80	$275.80
Purchase #5	$116.51	5.765%	$123.2268	$123.23	$123.25	$123.20
Purchase #6	$224.54	9.240%	$245.2875	$245.29	$245.30	$245.30
Purchase #7	$35.54	12.729%	$40.0639	$40.06	$40.05	$40.10
7 purchase totals =	$931.08		$1,025.1582	$1,025.15	$1,025.10	$1,025.20