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	$215.95	13.846%	$245.8504	$245.85	$245.85	$245.90
Purchase #2	$35.40	5.305%	$37.278	$37.28	$37.30	$37.30
Purchase #3	$115.29	7.219%	$123.6128	$123.61	$123.60	$123.60
Purchase #4	$62.88	11.496%	$70.1087	$70.11	$70.10	$70.10
Purchase #5	$168.91	6.551%	$179.9753	$179.98	$180.00	$180.00
Purchase #6	$64.55	12.762%	$72.7879	$72.79	$72.80	$72.80
Purchase #7	$22.60	6.825%	$24.1425	$24.14	$24.15	$24.10
7 purchase totals =	$685.58		$753.7556	$753.76	$753.80	$753.80