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	$138.29	13.845%	$157.4363	$157.44	$157.45	$157.40
Purchase #2	$173.70	7.272%	$186.3315	$186.33	$186.35	$186.30
Purchase #3	$31.96	8.214%	$34.5852	$34.59	$34.60	$34.60
Purchase #4	$157.45	7.669%	$169.5248	$169.52	$169.50	$169.50
Purchase #5	$154.74	11.318%	$172.2535	$172.25	$172.25	$172.30
Purchase #6	$59.37	4.274%	$61.9075	$61.91	$61.90	$61.90
Purchase #7	$5.72	13.229%	$6.4767	$6.48	$6.50	$6.50
7 purchase totals =	$721.23		$788.5155	$788.52	$788.55	$788.50