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	$175.99	5.287%	$185.2946	$185.29	$185.30	$185.30
Purchase #2	$97.59	6.550%	$103.9821	$103.98	$104.00	$104.00
Purchase #3	$11.56	4.724%	$12.1061	$12.11	$12.10	$12.10
Purchase #4	$92.98	11.773%	$103.9265	$103.93	$103.95	$103.90
Purchase #5	$140.28	11.776%	$156.7994	$156.80	$156.80	$156.80
Purchase #6	$205.75	7.414%	$221.0043	$221.00	$221.00	$221.00
Purchase #7	$172.54	7.364%	$185.2458	$185.25	$185.25	$185.20
7 purchase totals =	$896.69		$968.3588	$968.36	$968.40	$968.30