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	$93.83	7.478%	$100.8466	$100.85	$100.85	$100.80
Purchase #2	$19.37	6.789%	$20.685	$20.69	$20.70	$20.70
Purchase #3	$109.41	13.499%	$124.1793	$124.18	$124.20	$124.20
Purchase #4	$204.55	8.456%	$221.8467	$221.85	$221.85	$221.80
Purchase #5	$78.82	13.198%	$89.2227	$89.22	$89.20	$89.20
Purchase #6	$205.28	7.837%	$221.3678	$221.37	$221.35	$221.40
Purchase #7	$157.82	8.162%	$170.7013	$170.70	$170.70	$170.70
7 purchase totals =	$869.08		$948.8494	$948.86	$948.85	$948.80