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	$120.51	9.491%	$131.9476	$131.95	$131.95	$131.90
Purchase #2	$26.87	6.440%	$28.6004	$28.60	$28.60	$28.60
Purchase #3	$97.37	3.114%	$100.4021	$100.40	$100.40	$100.40
Purchase #4	$25.26	12.213%	$28.345	$28.35	$28.35	$28.30
Purchase #5	$70.55	4.446%	$73.6867	$73.69	$73.70	$73.70
Purchase #6	$18.82	6.501%	$20.0435	$20.04	$20.05	$20.00
Purchase #7	$101.41	8.301%	$109.828	$109.83	$109.85	$109.80
7 purchase totals =	$460.79		$492.8533	$492.86	$492.90	$492.70