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	$197.81	10.724%	$219.0231	$219.02	$219.00	$219.00
Purchase #2	$123.72	9.821%	$135.8705	$135.87	$135.85	$135.90
Purchase #3	$123.73	12.549%	$139.2569	$139.26	$139.25	$139.30
Purchase #4	$68.26	6.336%	$72.585	$72.59	$72.60	$72.60
Purchase #5	$24.88	13.143%	$28.15	$28.15	$28.15	$28.20
Purchase #6	$83.47	7.210%	$89.4882	$89.49	$89.50	$89.50
Purchase #7	$152.79	10.562%	$168.9277	$168.93	$168.95	$168.90
7 purchase totals =	$774.66		$853.3014	$853.31	$853.30	$853.40