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	$130.54	10.700%	$144.5078	$144.51	$144.50	$144.50
Purchase #2	$217.48	3.485%	$225.0592	$225.06	$225.05	$225.10
Purchase #3	$5.46	13.837%	$6.2155	$6.22	$6.20	$6.20
Purchase #4	$49.28	8.624%	$53.5299	$53.53	$53.55	$53.50
Purchase #5	$60.64	5.612%	$64.0431	$64.04	$64.05	$64.00
Purchase #6	$94.54	6.374%	$100.566	$100.57	$100.55	$100.60
Purchase #7	$135.52	4.321%	$141.3758	$141.38	$141.40	$141.40
7 purchase totals =	$693.46		$735.2973	$735.31	$735.30	$735.30