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	$139.46	4.450%	$145.666	$145.67	$145.65	$145.70
Purchase #2	$91.29	9.342%	$99.8183	$99.82	$99.80	$99.80
Purchase #3	$122.64	8.346%	$132.8755	$132.88	$132.90	$132.90
Purchase #4	$187.32	7.180%	$200.7696	$200.77	$200.75	$200.80
Purchase #5	$191.97	5.729%	$202.968	$202.97	$202.95	$203.00
Purchase #6	$35.64	11.434%	$39.7151	$39.72	$39.70	$39.70
Purchase #7	$241.97	11.539%	$269.8909	$269.89	$269.90	$269.90
7 purchase totals =	$1,010.29		$1,091.7034	$1,091.72	$1,091.65	$1,091.80