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	$155.36	8.397%	$168.4056	$168.41	$168.40	$168.40
Purchase #2	$205.48	6.147%	$218.1109	$218.11	$218.10	$218.10
Purchase #3	$132.90	7.303%	$142.6057	$142.61	$142.60	$142.60
Purchase #4	$110.78	12.591%	$124.7283	$124.73	$124.75	$124.70
Purchase #5	$95.43	8.188%	$103.2438	$103.24	$103.25	$103.20
Purchase #6	$50.89	11.422%	$56.7027	$56.70	$56.70	$56.70
Purchase #7	$224.62	5.700%	$237.4233	$237.42	$237.40	$237.40
7 purchase totals =	$975.46		$1,051.2203	$1,051.22	$1,051.20	$1,051.10