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	$50.97	4.640%	$53.335	$53.34	$53.35	$53.30
Purchase #2	$197.69	5.507%	$208.5768	$208.58	$208.60	$208.60
Purchase #3	$88.64	3.440%	$91.6892	$91.69	$91.70	$91.70
Purchase #4	$164.56	8.263%	$178.1576	$178.16	$178.15	$178.20
Purchase #5	$120.86	13.702%	$137.4202	$137.42	$137.40	$137.40
Purchase #6	$169.53	3.182%	$174.9244	$174.92	$174.90	$174.90
Purchase #7	$200.89	5.294%	$211.5251	$211.53	$211.55	$211.50
7 purchase totals =	$993.14		$1,055.6283	$1,055.64	$1,055.65	$1,055.60