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	$204.39	13.200%	$231.3695	$231.37	$231.35	$231.40
Purchase #2	$56.37	3.152%	$58.1468	$58.15	$58.15	$58.10
Purchase #3	$119.56	5.811%	$126.5076	$126.51	$126.50	$126.50
Purchase #4	$97.50	12.185%	$109.3804	$109.38	$109.40	$109.40
Purchase #5	$88.40	3.637%	$91.6151	$91.62	$91.60	$91.60
Purchase #6	$142.72	7.360%	$153.2242	$153.22	$153.20	$153.20
Purchase #7	$134.64	13.110%	$152.2913	$152.29	$152.30	$152.30
7 purchase totals =	$843.58		$922.5349	$922.54	$922.50	$922.50