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	$116.43	11.302%	$129.5889	$129.59	$129.60	$129.60
Purchase #2	$75.27	9.724%	$82.5893	$82.59	$82.60	$82.60
Purchase #3	$6.53	13.428%	$7.4068	$7.41	$7.40	$7.40
Purchase #4	$94.86	11.739%	$105.9956	$106.00	$106.00	$106.00
Purchase #5	$136.57	6.868%	$145.9496	$145.95	$145.95	$145.90
Purchase #6	$232.31	7.661%	$250.1073	$250.11	$250.10	$250.10
Purchase #7	$221.89	5.143%	$233.3018	$233.30	$233.30	$233.30
7 purchase totals =	$883.86		$954.9393	$954.95	$954.95	$954.90