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	$44.57	8.758%	$48.4734	$48.47	$48.45	$48.50
Purchase #2	$67.96	5.337%	$71.587	$71.59	$71.60	$71.60
Purchase #3	$73.30	6.631%	$78.1605	$78.16	$78.15	$78.20
Purchase #4	$133.55	11.600%	$149.0418	$149.04	$149.05	$149.00
Purchase #5	$80.50	11.695%	$89.9145	$89.91	$89.90	$89.90
Purchase #6	$45.84	8.351%	$49.6681	$49.67	$49.65	$49.70
Purchase #7	$36.79	4.153%	$38.3179	$38.32	$38.30	$38.30
7 purchase totals =	$482.51		$525.1632	$525.16	$525.10	$525.20