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	$231.58	4.445%	$241.8737	$241.87	$241.85	$241.90
Purchase #2	$77.47	10.105%	$85.2983	$85.30	$85.30	$85.30
Purchase #3	$125.34	6.655%	$133.6814	$133.68	$133.70	$133.70
Purchase #4	$191.89	13.263%	$217.3404	$217.34	$217.35	$217.30
Purchase #5	$57.52	12.237%	$64.5587	$64.56	$64.55	$64.60
Purchase #6	$163.34	6.106%	$173.3135	$173.31	$173.30	$173.30
Purchase #7	$171.82	10.170%	$189.2941	$189.29	$189.30	$189.30
7 purchase totals =	$1,018.96		$1,105.3601	$1,105.35	$1,105.35	$1,105.40