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	$151.62	7.654%	$163.225	$163.23	$163.25	$163.20
Purchase #2	$207.72	12.783%	$234.2728	$234.27	$234.25	$234.30
Purchase #3	$168.70	12.783%	$190.2649	$190.26	$190.25	$190.30
Purchase #4	$44.46	13.253%	$50.3523	$50.35	$50.35	$50.40
Purchase #5	$35.84	3.505%	$37.0962	$37.10	$37.10	$37.10
Purchase #6	$167.47	13.219%	$189.6079	$189.61	$189.60	$189.60
Purchase #7	$166.56	9.555%	$182.4748	$182.47	$182.45	$182.50
7 purchase totals =	$942.37		$1,047.2939	$1,047.29	$1,047.25	$1,047.40