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	$162.48	13.863%	$185.0046	$185.00	$185.00	$185.00
Purchase #2	$163.57	5.640%	$172.7953	$172.80	$172.80	$172.80
Purchase #3	$57.66	8.114%	$62.3385	$62.34	$62.35	$62.30
Purchase #4	$206.66	11.208%	$229.8225	$229.82	$229.80	$229.80
Purchase #5	$238.77	5.113%	$250.9783	$250.98	$251.00	$251.00
Purchase #6	$221.27	7.746%	$238.4096	$238.41	$238.40	$238.40
Purchase #7	$105.40	6.312%	$112.0528	$112.05	$112.05	$112.10
7 purchase totals =	$1,155.81		$1,251.4016	$1,251.40	$1,251.40	$1,251.40