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	$185.42	10.183%	$204.3013	$204.30	$204.30	$204.30
Purchase #2	$22.46	7.150%	$24.0659	$24.07	$24.05	$24.10
Purchase #3	$218.33	3.361%	$225.6681	$225.67	$225.65	$225.70
Purchase #4	$234.82	13.146%	$265.6894	$265.69	$265.70	$265.70
Purchase #5	$178.57	6.415%	$190.0253	$190.03	$190.05	$190.00
Purchase #6	$243.64	8.725%	$264.8976	$264.90	$264.90	$264.90
Purchase #7	$200.27	11.792%	$223.8858	$223.89	$223.90	$223.90
7 purchase totals =	$1,283.51		$1,398.5334	$1,398.55	$1,398.55	$1,398.60