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	$214.93	7.644%	$231.3592	$231.36	$231.35	$231.40
Purchase #2	$159.35	13.488%	$180.8431	$180.84	$180.85	$180.80
Purchase #3	$79.92	12.179%	$89.6535	$89.65	$89.65	$89.70
Purchase #4	$243.97	4.667%	$255.3561	$255.36	$255.35	$255.40
Purchase #5	$42.29	12.102%	$47.4079	$47.41	$47.40	$47.40
Purchase #6	$99.56	13.665%	$113.1649	$113.16	$113.15	$113.20
Purchase #7	$92.98	6.513%	$99.0358	$99.04	$99.05	$99.00
7 purchase totals =	$933.00		$1,016.8205	$1,016.82	$1,016.80	$1,016.90