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	$148.66	5.507%	$156.8467	$156.85	$156.85	$156.80
Purchase #2	$172.93	9.850%	$189.9636	$189.96	$189.95	$190.00
Purchase #3	$79.92	11.425%	$89.0509	$89.05	$89.05	$89.10
Purchase #4	$198.38	12.848%	$223.8679	$223.87	$223.85	$223.90
Purchase #5	$156.41	4.474%	$163.4078	$163.41	$163.40	$163.40
Purchase #6	$208.45	7.304%	$223.6752	$223.68	$223.70	$223.70
Purchase #7	$102.41	3.319%	$105.809	$105.81	$105.80	$105.80
7 purchase totals =	$1,067.16		$1,152.6211	$1,152.63	$1,152.60	$1,152.70