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	$85.99	3.769%	$89.231	$89.23	$89.25	$89.20
Purchase #2	$21.53	3.332%	$22.2474	$22.25	$22.25	$22.20
Purchase #3	$197.28	7.205%	$211.494	$211.49	$211.50	$211.50
Purchase #4	$185.54	8.134%	$200.6318	$200.63	$200.65	$200.60
Purchase #5	$200.64	12.826%	$226.3741	$226.37	$226.35	$226.40
Purchase #6	$240.39	10.306%	$265.1646	$265.16	$265.15	$265.20
Purchase #7	$66.69	7.282%	$71.5464	$71.55	$71.55	$71.50
7 purchase totals =	$998.06		$1,086.6893	$1,086.68	$1,086.70	$1,086.60