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	$78.53	9.184%	$85.7422	$85.74	$85.75	$85.70
Purchase #2	$156.74	5.478%	$165.3262	$165.33	$165.35	$165.30
Purchase #3	$190.32	11.432%	$212.0774	$212.08	$212.10	$212.10
Purchase #4	$221.69	7.292%	$237.8556	$237.86	$237.85	$237.90
Purchase #5	$76.41	6.204%	$81.1505	$81.15	$81.15	$81.20
Purchase #6	$93.34	11.489%	$104.0638	$104.06	$104.05	$104.10
Purchase #7	$153.86	9.696%	$168.7783	$168.78	$168.80	$168.80
7 purchase totals =	$970.89		$1,054.9940	$1,055.00	$1,055.05	$1,055.10