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	$169.81	9.441%	$185.8418	$185.84	$185.85	$185.80
Purchase #2	$75.25	11.440%	$83.8586	$83.86	$83.85	$83.90
Purchase #3	$162.49	8.208%	$175.8272	$175.83	$175.85	$175.80
Purchase #4	$19.89	12.647%	$22.4055	$22.41	$22.40	$22.40
Purchase #5	$196.91	13.446%	$223.3865	$223.39	$223.40	$223.40
Purchase #6	$232.39	9.240%	$253.8628	$253.86	$253.85	$253.90
Purchase #7	$122.62	3.778%	$127.2526	$127.25	$127.25	$127.30
7 purchase totals =	$979.36		$1,072.4350	$1,072.44	$1,072.45	$1,072.50