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	$161.54	4.380%	$168.6155	$168.62	$168.60	$168.60
Purchase #2	$202.34	11.662%	$225.9369	$225.94	$225.95	$225.90
Purchase #3	$248.86	13.377%	$282.15	$282.15	$282.15	$282.20
Purchase #4	$159.48	7.400%	$171.2815	$171.28	$171.30	$171.30
Purchase #5	$175.57	13.114%	$198.5942	$198.59	$198.60	$198.60
Purchase #6	$158.60	4.856%	$166.3016	$166.30	$166.30	$166.30
Purchase #7	$171.62	12.815%	$193.6131	$193.61	$193.60	$193.60
7 purchase totals =	$1,278.01		$1,406.4928	$1,406.49	$1,406.50	$1,406.50