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	$50.51	3.752%	$52.4051	$52.41	$52.40	$52.40
Purchase #2	$87.29	5.123%	$91.7619	$91.76	$91.75	$91.80
Purchase #3	$215.25	5.840%	$227.8206	$227.82	$227.80	$227.80
Purchase #4	$169.27	11.752%	$189.1626	$189.16	$189.15	$189.20
Purchase #5	$180.51	8.735%	$196.2775	$196.28	$196.30	$196.30
Purchase #6	$23.76	10.116%	$26.1636	$26.16	$26.15	$26.20
Purchase #7	$233.25	9.632%	$255.7166	$255.72	$255.70	$255.70
7 purchase totals =	$959.84		$1,039.3079	$1,039.31	$1,039.25	$1,039.40