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	$44.28	5.135%	$46.5538	$46.55	$46.55	$46.60
Purchase #2	$94.36	11.759%	$105.4558	$105.46	$105.45	$105.50
Purchase #3	$170.88	6.591%	$182.1427	$182.14	$182.15	$182.10
Purchase #4	$134.26	12.773%	$151.409	$151.41	$151.40	$151.40
Purchase #5	$64.93	10.856%	$71.9788	$71.98	$72.00	$72.00
Purchase #6	$14.93	3.848%	$15.5045	$15.50	$15.50	$15.50
Purchase #7	$154.76	8.446%	$167.831	$167.83	$167.85	$167.80
7 purchase totals =	$678.40		$740.8756	$740.87	$740.90	$740.90