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	$123.28	4.461%	$128.7795	$128.78	$128.80	$128.80
Purchase #2	$67.97	4.592%	$71.0912	$71.09	$71.10	$71.10
Purchase #3	$7.67	4.737%	$8.0333	$8.03	$8.05	$8.00
Purchase #4	$206.46	12.171%	$231.5882	$231.59	$231.60	$231.60
Purchase #5	$171.45	4.763%	$179.6162	$179.62	$179.60	$179.60
Purchase #6	$47.76	5.665%	$50.4656	$50.47	$50.45	$50.50
Purchase #7	$165.26	12.264%	$185.5275	$185.53	$185.55	$185.50
7 purchase totals =	$789.85		$855.1015	$855.11	$855.15	$855.10