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	$46.58	13.760%	$52.9894	$52.99	$53.00	$53.00
Purchase #2	$173.26	4.490%	$181.0394	$181.04	$181.05	$181.00
Purchase #3	$229.61	12.590%	$258.5179	$258.52	$258.50	$258.50
Purchase #4	$147.82	8.850%	$160.9021	$160.90	$160.90	$160.90
Purchase #5	$196.62	9.234%	$214.7759	$214.78	$214.80	$214.80
Purchase #6	$99.31	4.557%	$103.8356	$103.84	$103.85	$103.80
Purchase #7	$117.46	5.317%	$123.7053	$123.71	$123.70	$123.70
7 purchase totals =	$1,010.66		$1,095.7656	$1,095.78	$1,095.80	$1,095.70