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	$164.59	12.135%	$184.563	$184.56	$184.55	$184.60
Purchase #2	$167.51	4.369%	$174.8285	$174.83	$174.85	$174.80
Purchase #3	$126.94	13.322%	$143.8509	$143.85	$143.85	$143.90
Purchase #4	$164.87	4.861%	$172.8843	$172.88	$172.90	$172.90
Purchase #5	$52.74	6.386%	$56.108	$56.11	$56.10	$56.10
Purchase #6	$149.58	13.503%	$169.7778	$169.78	$169.80	$169.80
Purchase #7	$245.56	6.706%	$262.0273	$262.03	$262.05	$262.00
7 purchase totals =	$1,071.79		$1,164.0398	$1,164.04	$1,164.10	$1,164.10