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	$123.32	5.648%	$130.2851	$130.29	$130.30	$130.30
Purchase #2	$18.64	8.221%	$20.1724	$20.17	$20.15	$20.20
Purchase #3	$209.37	13.433%	$237.4947	$237.49	$237.50	$237.50
Purchase #4	$5.97	6.771%	$6.3742	$6.37	$6.35	$6.40
Purchase #5	$86.64	5.810%	$91.6738	$91.67	$91.65	$91.70
Purchase #6	$77.78	12.217%	$87.2824	$87.28	$87.30	$87.30
Purchase #7	$52.89	3.166%	$54.5645	$54.56	$54.55	$54.60
7 purchase totals =	$574.61		$627.8471	$627.83	$627.80	$628.00