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	$86.27	3.538%	$89.3222	$89.32	$89.30	$89.30
Purchase #2	$11.27	10.594%	$12.4639	$12.46	$12.45	$12.50
Purchase #3	$242.47	6.359%	$257.8887	$257.89	$257.90	$257.90
Purchase #4	$181.25	6.378%	$192.8101	$192.81	$192.80	$192.80
Purchase #5	$248.36	3.106%	$256.0741	$256.07	$256.05	$256.10
Purchase #6	$89.29	11.777%	$99.8057	$99.81	$99.80	$99.80
Purchase #7	$125.36	11.860%	$140.2277	$140.23	$140.25	$140.20
7 purchase totals =	$984.27		$1,048.5924	$1,048.59	$1,048.55	$1,048.60