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	$215.30	5.769%	$227.7207	$227.72	$227.70	$227.70
Purchase #2	$12.61	3.821%	$13.0918	$13.09	$13.10	$13.10
Purchase #3	$82.86	9.699%	$90.8966	$90.90	$90.90	$90.90
Purchase #4	$53.52	9.679%	$58.7002	$58.70	$58.70	$58.70
Purchase #5	$55.53	7.409%	$59.6442	$59.64	$59.65	$59.60
Purchase #6	$221.58	12.849%	$250.0508	$250.05	$250.05	$250.10
Purchase #7	$29.43	3.780%	$30.5425	$30.54	$30.55	$30.50
7 purchase totals =	$670.83		$730.6468	$730.64	$730.65	$730.60