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	$131.61	13.192%	$148.972	$148.97	$148.95	$149.00
Purchase #2	$103.31	11.152%	$114.8311	$114.83	$114.85	$114.80
Purchase #3	$97.79	12.228%	$109.7478	$109.75	$109.75	$109.70
Purchase #4	$224.76	13.679%	$255.5049	$255.50	$255.50	$255.50
Purchase #5	$119.28	9.511%	$130.6247	$130.62	$130.60	$130.60
Purchase #6	$89.77	5.592%	$94.7899	$94.79	$94.80	$94.80
Purchase #7	$134.52	5.755%	$142.2616	$142.26	$142.25	$142.30
7 purchase totals =	$901.04		$996.7320	$996.72	$996.70	$996.70