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	$106.72	7.123%	$114.3217	$114.32	$114.30	$114.30
Purchase #2	$83.93	9.367%	$91.7917	$91.79	$91.80	$91.80
Purchase #3	$63.93	3.700%	$66.2954	$66.30	$66.30	$66.30
Purchase #4	$221.74	4.192%	$231.0353	$231.04	$231.05	$231.00
Purchase #5	$241.32	9.251%	$263.6445	$263.64	$263.65	$263.60
Purchase #6	$167.61	7.594%	$180.3383	$180.34	$180.35	$180.30
Purchase #7	$119.56	3.419%	$123.6478	$123.65	$123.65	$123.60
7 purchase totals =	$1,004.81		$1,071.0747	$1,071.08	$1,071.10	$1,070.90