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	$176.25	5.328%	$185.6406	$185.64	$185.65	$185.60
Purchase #2	$91.57	6.302%	$97.3407	$97.34	$97.35	$97.30
Purchase #3	$245.91	12.296%	$276.1471	$276.15	$276.15	$276.10
Purchase #4	$133.33	4.641%	$139.5178	$139.52	$139.50	$139.50
Purchase #5	$250.63	9.465%	$274.3521	$274.35	$274.35	$274.40
Purchase #6	$10.82	10.581%	$11.9649	$11.96	$11.95	$12.00
Purchase #7	$92.50	5.222%	$97.3304	$97.33	$97.35	$97.30
7 purchase totals =	$1,001.01		$1,082.2936	$1,082.29	$1,082.30	$1,082.20