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	$120.73	6.164%	$128.1718	$128.17	$128.15	$128.20
Purchase #2	$12.45	10.789%	$13.7932	$13.79	$13.80	$13.80
Purchase #3	$168.50	12.708%	$189.913	$189.91	$189.90	$189.90
Purchase #4	$185.61	7.769%	$200.03	$200.03	$200.05	$200.00
Purchase #5	$188.31	4.316%	$196.4375	$196.44	$196.45	$196.40
Purchase #6	$147.79	6.791%	$157.8264	$157.83	$157.85	$157.80
Purchase #7	$137.41	6.633%	$146.5244	$146.52	$146.50	$146.50
7 purchase totals =	$960.80		$1,032.6963	$1,032.69	$1,032.70	$1,032.60