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	$114.36	11.268%	$127.2461	$127.25	$127.25	$127.20
Purchase #2	$123.57	4.150%	$128.6982	$128.70	$128.70	$128.70
Purchase #3	$80.35	7.502%	$86.3779	$86.38	$86.40	$86.40
Purchase #4	$105.37	7.388%	$113.1547	$113.15	$113.15	$113.20
Purchase #5	$141.61	11.463%	$157.8428	$157.84	$157.85	$157.80
Purchase #6	$136.55	4.436%	$142.6074	$142.61	$142.60	$142.60
Purchase #7	$223.31	12.267%	$250.7034	$250.70	$250.70	$250.70
7 purchase totals =	$925.12		$1,006.6305	$1,006.63	$1,006.65	$1,006.60