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	$171.70	11.785%	$191.9348	$191.93	$191.95	$191.90
Purchase #2	$181.42	6.540%	$193.2849	$193.28	$193.30	$193.30
Purchase #3	$170.37	3.857%	$176.9412	$176.94	$176.95	$176.90
Purchase #4	$180.92	8.356%	$196.0377	$196.04	$196.05	$196.00
Purchase #5	$31.78	12.780%	$35.8415	$35.84	$35.85	$35.80
Purchase #6	$121.78	7.829%	$131.3142	$131.31	$131.30	$131.30
Purchase #7	$84.57	12.648%	$95.2664	$95.27	$95.25	$95.30
7 purchase totals =	$942.54		$1,020.6207	$1,020.61	$1,020.65	$1,020.50