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	$138.32	13.224%	$156.6114	$156.61	$156.60	$156.60
Purchase #2	$94.34	5.508%	$99.5362	$99.54	$99.55	$99.50
Purchase #3	$123.82	9.309%	$135.3464	$135.35	$135.35	$135.30
Purchase #4	$53.36	4.310%	$55.6598	$55.66	$55.65	$55.70
Purchase #5	$70.53	4.533%	$73.7271	$73.73	$73.75	$73.70
Purchase #6	$186.48	5.112%	$196.0129	$196.01	$196.00	$196.00
Purchase #7	$146.39	13.133%	$165.6154	$165.62	$165.60	$165.60
7 purchase totals =	$813.24		$882.5092	$882.52	$882.50	$882.40