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	$131.81	7.814%	$142.1096	$142.11	$142.10	$142.10
Purchase #2	$180.39	10.402%	$199.1542	$199.15	$199.15	$199.20
Purchase #3	$78.75	12.661%	$88.7205	$88.72	$88.70	$88.70
Purchase #4	$198.56	8.532%	$215.5011	$215.50	$215.50	$215.50
Purchase #5	$129.54	12.793%	$146.1121	$146.11	$146.10	$146.10
Purchase #6	$179.87	8.315%	$194.8262	$194.83	$194.85	$194.80
Purchase #7	$32.33	10.343%	$35.6739	$35.67	$35.65	$35.70
7 purchase totals =	$931.25		$1,022.0976	$1,022.09	$1,022.05	$1,022.10