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	$116.56	9.636%	$127.7917	$127.79	$127.80	$127.80
Purchase #2	$245.53	4.569%	$256.7483	$256.75	$256.75	$256.70
Purchase #3	$163.27	9.699%	$179.1056	$179.11	$179.10	$179.10
Purchase #4	$141.33	11.564%	$157.6734	$157.67	$157.65	$157.70
Purchase #5	$127.30	13.445%	$144.4155	$144.42	$144.40	$144.40
Purchase #6	$121.64	7.588%	$130.87	$130.87	$130.85	$130.90
Purchase #7	$78.47	12.579%	$88.3407	$88.34	$88.35	$88.30
7 purchase totals =	$994.10		$1,084.9452	$1,084.95	$1,084.90	$1,084.90