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	$246.89	4.807%	$258.758	$258.76	$258.75	$258.80
Purchase #2	$179.43	6.630%	$191.3262	$191.33	$191.35	$191.30
Purchase #3	$105.47	4.776%	$110.5072	$110.51	$110.50	$110.50
Purchase #4	$250.74	13.728%	$285.1616	$285.16	$285.15	$285.20
Purchase #5	$195.38	12.327%	$219.4645	$219.46	$219.45	$219.50
Purchase #6	$199.80	8.479%	$216.741	$216.74	$216.75	$216.70
Purchase #7	$77.83	5.457%	$82.0772	$82.08	$82.10	$82.10
7 purchase totals =	$1,255.54		$1,364.0357	$1,364.04	$1,364.05	$1,364.10