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	$68.39	5.388%	$72.0749	$72.07	$72.05	$72.10
Purchase #2	$82.33	8.519%	$89.3437	$89.34	$89.35	$89.30
Purchase #3	$243.91	8.170%	$263.8374	$263.84	$263.85	$263.80
Purchase #4	$248.79	4.141%	$259.0924	$259.09	$259.10	$259.10
Purchase #5	$104.34	13.822%	$118.7619	$118.76	$118.75	$118.80
Purchase #6	$72.42	4.552%	$75.7166	$75.72	$75.70	$75.70
Purchase #7	$242.92	11.858%	$271.7255	$271.73	$271.75	$271.70
7 purchase totals =	$1,063.10		$1,150.5524	$1,150.55	$1,150.55	$1,150.50