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	$150.72	3.160%	$155.4828	$155.48	$155.50	$155.50
Purchase #2	$71.85	12.512%	$80.8399	$80.84	$80.85	$80.80
Purchase #3	$245.51	5.849%	$259.8699	$259.87	$259.85	$259.90
Purchase #4	$217.60	5.625%	$229.84	$229.84	$229.85	$229.80
Purchase #5	$233.89	3.373%	$241.7791	$241.78	$241.80	$241.80
Purchase #6	$127.36	11.403%	$141.8829	$141.88	$141.90	$141.90
Purchase #7	$236.49	7.220%	$253.5646	$253.56	$253.55	$253.60
7 purchase totals =	$1,283.42		$1,363.2592	$1,363.25	$1,363.30	$1,363.30