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	$212.55	7.721%	$228.961	$228.96	$228.95	$229.00
Purchase #2	$147.51	3.400%	$152.5253	$152.53	$152.55	$152.50
Purchase #3	$47.34	9.371%	$51.7762	$51.78	$51.80	$51.80
Purchase #4	$202.77	7.722%	$218.4279	$218.43	$218.45	$218.40
Purchase #5	$36.46	11.861%	$40.7845	$40.78	$40.80	$40.80
Purchase #6	$143.73	4.119%	$149.6502	$149.65	$149.65	$149.70
Purchase #7	$66.46	9.316%	$72.6514	$72.65	$72.65	$72.70
7 purchase totals =	$856.82		$914.7765	$914.78	$914.85	$914.90