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	$130.77	8.275%	$141.5912	$141.59	$141.60	$141.60
Purchase #2	$181.36	6.322%	$192.8256	$192.83	$192.85	$192.80
Purchase #3	$148.64	11.391%	$165.5716	$165.57	$165.55	$165.60
Purchase #4	$71.79	7.386%	$77.0924	$77.09	$77.10	$77.10
Purchase #5	$193.57	13.728%	$220.1433	$220.14	$220.15	$220.10
Purchase #6	$54.99	8.239%	$59.5206	$59.52	$59.50	$59.50
Purchase #7	$204.47	3.279%	$211.1746	$211.17	$211.15	$211.20
7 purchase totals =	$985.59		$1,067.9193	$1,067.91	$1,067.90	$1,067.90