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	$140.82	7.119%	$150.845	$150.85	$150.85	$150.80
Purchase #2	$28.28	5.399%	$29.8068	$29.81	$29.80	$29.80
Purchase #3	$122.77	4.321%	$128.0749	$128.07	$128.05	$128.10
Purchase #4	$168.41	10.771%	$186.5494	$186.55	$186.55	$186.50
Purchase #5	$226.25	5.566%	$238.8431	$238.84	$238.85	$238.80
Purchase #6	$31.89	6.472%	$33.9539	$33.95	$33.95	$34.00
Purchase #7	$211.80	7.763%	$228.242	$228.24	$228.25	$228.20
7 purchase totals =	$930.22		$996.3151	$996.31	$996.30	$996.20