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	$77.45	12.162%	$86.8695	$86.87	$86.85	$86.90
Purchase #2	$17.28	8.759%	$18.7936	$18.79	$18.80	$18.80
Purchase #3	$82.49	9.199%	$90.0783	$90.08	$90.10	$90.10
Purchase #4	$165.76	9.549%	$181.5884	$181.59	$181.60	$181.60
Purchase #5	$65.58	12.753%	$73.9434	$73.94	$73.95	$73.90
Purchase #6	$243.92	7.370%	$261.8969	$261.90	$261.90	$261.90
Purchase #7	$143.62	5.647%	$151.7302	$151.73	$151.75	$151.70
7 purchase totals =	$796.10		$864.9003	$864.90	$864.95	$864.90