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	$31.80	12.397%	$35.7422	$35.74	$35.75	$35.70
Purchase #2	$58.74	7.784%	$63.3123	$63.31	$63.30	$63.30
Purchase #3	$108.33	13.778%	$123.2557	$123.26	$123.25	$123.30
Purchase #4	$67.72	12.393%	$76.1125	$76.11	$76.10	$76.10
Purchase #5	$166.99	5.678%	$176.4717	$176.47	$176.45	$176.50
Purchase #6	$71.37	10.601%	$78.9359	$78.94	$78.95	$78.90
Purchase #7	$94.38	5.682%	$99.7427	$99.74	$99.75	$99.70
7 purchase totals =	$599.33		$653.5730	$653.57	$653.55	$653.50