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	$101.36	10.345%	$111.8457	$111.85	$111.85	$111.80
Purchase #2	$209.37	9.613%	$229.4967	$229.50	$229.50	$229.50
Purchase #3	$195.87	13.275%	$221.8717	$221.87	$221.85	$221.90
Purchase #4	$200.69	12.651%	$226.0793	$226.08	$226.10	$226.10
Purchase #5	$41.67	11.834%	$46.6012	$46.60	$46.60	$46.60
Purchase #6	$142.53	7.261%	$152.8791	$152.88	$152.90	$152.90
Purchase #7	$60.43	8.827%	$65.7642	$65.76	$65.75	$65.80
7 purchase totals =	$951.92		$1,054.5379	$1,054.54	$1,054.55	$1,054.60