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	$93.52	8.648%	$101.6076	$101.61	$101.60	$101.60
Purchase #2	$7.68	5.792%	$8.1248	$8.12	$8.10	$8.10
Purchase #3	$80.98	11.802%	$90.5373	$90.54	$90.55	$90.50
Purchase #4	$30.93	10.848%	$34.2853	$34.29	$34.30	$34.30
Purchase #5	$47.40	10.545%	$52.3983	$52.40	$52.40	$52.40
Purchase #6	$178.56	10.774%	$197.7981	$197.80	$197.80	$197.80
Purchase #7	$83.76	7.836%	$90.3234	$90.32	$90.30	$90.30
7 purchase totals =	$522.83		$575.0748	$575.08	$575.05	$575.00