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	$117.43	10.470%	$129.7249	$129.72	$129.70	$129.70
Purchase #2	$29.41	10.311%	$32.4425	$32.44	$32.45	$32.40
Purchase #3	$120.74	6.519%	$128.611	$128.61	$128.60	$128.60
Purchase #4	$56.89	3.820%	$59.0632	$59.06	$59.05	$59.10
Purchase #5	$182.45	5.707%	$192.8624	$192.86	$192.85	$192.90
Purchase #6	$183.42	7.466%	$197.1141	$197.11	$197.10	$197.10
Purchase #7	$91.72	3.528%	$94.9559	$94.96	$94.95	$95.00
7 purchase totals =	$782.06		$834.7740	$834.76	$834.70	$834.80