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	$189.61	5.212%	$199.4925	$199.49	$199.50	$199.50
Purchase #2	$129.76	8.185%	$140.3809	$140.38	$140.40	$140.40
Purchase #3	$89.67	13.725%	$101.9772	$101.98	$102.00	$102.00
Purchase #4	$189.57	3.668%	$196.5234	$196.52	$196.50	$196.50
Purchase #5	$86.27	6.850%	$92.1795	$92.18	$92.20	$92.20
Purchase #6	$210.86	3.388%	$218.0039	$218.00	$218.00	$218.00
Purchase #7	$196.82	6.592%	$209.7944	$209.79	$209.80	$209.80
7 purchase totals =	$1,092.56		$1,158.3518	$1,158.34	$1,158.40	$1,158.40