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	$116.68	12.869%	$131.6955	$131.70	$131.70	$131.70
Purchase #2	$89.87	7.345%	$96.471	$96.47	$96.45	$96.50
Purchase #3	$105.45	5.784%	$111.5492	$111.55	$111.55	$111.50
Purchase #4	$176.32	4.780%	$184.7481	$184.75	$184.75	$184.70
Purchase #5	$250.52	5.788%	$265.0201	$265.02	$265.00	$265.00
Purchase #6	$35.89	3.414%	$37.1153	$37.12	$37.10	$37.10
Purchase #7	$78.62	9.596%	$86.1644	$86.16	$86.15	$86.20
7 purchase totals =	$853.35		$912.7636	$912.77	$912.70	$912.70