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	$139.88	6.437%	$148.8841	$148.88	$148.90	$148.90
Purchase #2	$238.92	12.613%	$269.055	$269.06	$269.05	$269.10
Purchase #3	$77.73	10.498%	$85.8901	$85.89	$85.90	$85.90
Purchase #4	$71.78	13.867%	$81.7337	$81.73	$81.75	$81.70
Purchase #5	$133.94	9.187%	$146.2451	$146.25	$146.25	$146.20
Purchase #6	$43.74	9.371%	$47.8389	$47.84	$47.85	$47.80
Purchase #7	$167.46	3.576%	$173.4484	$173.45	$173.45	$173.40
7 purchase totals =	$873.45		$953.0953	$953.10	$953.15	$953.00