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	$140.71	7.198%	$150.8383	$150.84	$150.85	$150.80
Purchase #2	$138.76	12.193%	$155.679	$155.68	$155.70	$155.70
Purchase #3	$101.96	7.701%	$109.8119	$109.81	$109.80	$109.80
Purchase #4	$111.88	6.260%	$118.8837	$118.88	$118.90	$118.90
Purchase #5	$56.99	12.794%	$64.2813	$64.28	$64.30	$64.30
Purchase #6	$65.72	10.651%	$72.7198	$72.72	$72.70	$72.70
Purchase #7	$30.76	10.160%	$33.8852	$33.89	$33.90	$33.90
7 purchase totals =	$646.78		$706.0992	$706.10	$706.15	$706.10