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	$83.47	10.820%	$92.5015	$92.50	$92.50	$92.50
Purchase #2	$60.38	10.122%	$66.4917	$66.49	$66.50	$66.50
Purchase #3	$42.48	8.620%	$46.1418	$46.14	$46.15	$46.10
Purchase #4	$6.47	13.132%	$7.3196	$7.32	$7.30	$7.30
Purchase #5	$27.98	7.727%	$30.142	$30.14	$30.15	$30.10
Purchase #6	$238.78	5.255%	$251.3279	$251.33	$251.35	$251.30
Purchase #7	$6.52	13.274%	$7.3855	$7.39	$7.40	$7.40
7 purchase totals =	$466.08		$501.3100	$501.31	$501.35	$501.20