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	$74.69	10.811%	$82.7647	$82.76	$82.75	$82.80
Purchase #2	$165.72	8.579%	$179.9371	$179.94	$179.95	$179.90
Purchase #3	$226.56	5.113%	$238.144	$238.14	$238.15	$238.10
Purchase #4	$199.70	9.458%	$218.5876	$218.59	$218.60	$218.60
Purchase #5	$177.70	3.769%	$184.3975	$184.40	$184.40	$184.40
Purchase #6	$152.46	8.482%	$165.3917	$165.39	$165.40	$165.40
Purchase #7	$214.60	3.284%	$221.6475	$221.65	$221.65	$221.60
7 purchase totals =	$1,211.43		$1,290.8701	$1,290.87	$1,290.90	$1,290.80