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	$60.30	11.669%	$67.3364	$67.34	$67.35	$67.30
Purchase #2	$242.55	6.104%	$257.3553	$257.36	$257.35	$257.40
Purchase #3	$135.64	11.772%	$151.6075	$151.61	$151.60	$151.60
Purchase #4	$112.93	5.272%	$118.8837	$118.88	$118.90	$118.90
Purchase #5	$71.33	9.573%	$78.1584	$78.16	$78.15	$78.20
Purchase #6	$82.47	5.253%	$86.8021	$86.80	$86.80	$86.80
Purchase #7	$180.41	6.652%	$192.4109	$192.41	$192.40	$192.40
7 purchase totals =	$885.63		$952.5543	$952.56	$952.55	$952.60