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	$57.51	5.524%	$60.6869	$60.69	$60.70	$60.70
Purchase #2	$99.77	9.565%	$109.313	$109.31	$109.30	$109.30
Purchase #3	$50.50	5.734%	$53.3957	$53.40	$53.40	$53.40
Purchase #4	$150.78	4.641%	$157.7777	$157.78	$157.80	$157.80
Purchase #5	$53.83	13.817%	$61.2677	$61.27	$61.25	$61.30
Purchase #6	$239.27	4.439%	$249.8912	$249.89	$249.90	$249.90
Purchase #7	$215.97	10.571%	$238.8002	$238.80	$238.80	$238.80
7 purchase totals =	$867.63		$931.1324	$931.14	$931.15	$931.20