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	$99.89	5.122%	$105.0064	$105.01	$105.00	$105.00
Purchase #2	$9.76	4.542%	$10.2033	$10.20	$10.20	$10.20
Purchase #3	$89.77	11.694%	$100.2677	$100.27	$100.25	$100.30
Purchase #4	$46.61	10.587%	$51.5446	$51.54	$51.55	$51.50
Purchase #5	$107.78	4.424%	$112.5482	$112.55	$112.55	$112.50
Purchase #6	$35.66	3.779%	$37.0076	$37.01	$37.00	$37.00
Purchase #7	$113.70	4.754%	$119.1053	$119.11	$119.10	$119.10
7 purchase totals =	$503.17		$535.6831	$535.69	$535.65	$535.60