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	$33.98	3.167%	$35.0561	$35.06	$35.05	$35.10
Purchase #2	$46.52	3.392%	$48.098	$48.10	$48.10	$48.10
Purchase #3	$72.87	7.419%	$78.2762	$78.28	$78.30	$78.30
Purchase #4	$117.93	5.107%	$123.9527	$123.95	$123.95	$124.00
Purchase #5	$154.45	11.140%	$171.6557	$171.66	$171.65	$171.70
Purchase #6	$247.66	9.113%	$270.2293	$270.23	$270.25	$270.20
Purchase #7	$231.59	12.204%	$259.8532	$259.85	$259.85	$259.90
7 purchase totals =	$905.00		$987.1212	$987.13	$987.15	$987.30