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	$63.42	13.182%	$71.78	$71.78	$71.80	$71.80
Purchase #2	$89.42	12.169%	$100.3015	$100.30	$100.30	$100.30
Purchase #3	$25.70	4.668%	$26.8997	$26.90	$26.90	$26.90
Purchase #4	$166.35	12.676%	$187.4365	$187.44	$187.45	$187.40
Purchase #5	$62.72	12.340%	$70.4596	$70.46	$70.45	$70.50
Purchase #6	$138.38	11.382%	$154.1304	$154.13	$154.15	$154.10
Purchase #7	$158.30	13.802%	$180.1486	$180.15	$180.15	$180.10
7 purchase totals =	$704.29		$791.1563	$791.16	$791.20	$791.10