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	$83.81	13.560%	$95.1746	$95.17	$95.15	$95.20
Purchase #2	$134.28	8.444%	$145.6186	$145.62	$145.60	$145.60
Purchase #3	$71.85	8.712%	$78.1096	$78.11	$78.10	$78.10
Purchase #4	$40.37	4.402%	$42.1471	$42.15	$42.15	$42.10
Purchase #5	$190.77	11.407%	$212.5311	$212.53	$212.55	$212.50
Purchase #6	$90.99	8.165%	$98.4193	$98.42	$98.40	$98.40
Purchase #7	$12.98	12.452%	$14.5963	$14.60	$14.60	$14.60
7 purchase totals =	$625.05		$686.5966	$686.60	$686.55	$686.50