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	$233.34	7.457%	$250.7402	$250.74	$250.75	$250.70
Purchase #2	$213.54	13.498%	$242.3636	$242.36	$242.35	$242.40
Purchase #3	$76.94	6.448%	$81.9011	$81.90	$81.90	$81.90
Purchase #4	$111.91	13.620%	$127.1521	$127.15	$127.15	$127.20
Purchase #5	$33.95	11.587%	$37.8838	$37.88	$37.90	$37.90
Purchase #6	$204.56	5.279%	$215.3587	$215.36	$215.35	$215.40
Purchase #7	$174.60	3.440%	$180.6062	$180.61	$180.60	$180.60
7 purchase totals =	$1,048.84		$1,136.0057	$1,136.00	$1,136.00	$1,136.10