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	$238.56	12.365%	$268.0579	$268.06	$268.05	$268.10
Purchase #2	$236.53	12.873%	$266.9785	$266.98	$267.00	$267.00
Purchase #3	$92.61	8.251%	$100.2513	$100.25	$100.25	$100.30
Purchase #4	$78.99	7.821%	$85.1678	$85.17	$85.15	$85.20
Purchase #5	$42.61	3.861%	$44.2552	$44.26	$44.25	$44.30
Purchase #6	$45.75	12.189%	$51.3265	$51.33	$51.35	$51.30
Purchase #7	$73.30	11.112%	$81.4451	$81.45	$81.45	$81.40
7 purchase totals =	$808.35		$897.4823	$897.50	$897.50	$897.60