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	$110.50	11.444%	$123.1456	$123.15	$123.15	$123.10
Purchase #2	$110.75	3.231%	$114.3283	$114.33	$114.35	$114.30
Purchase #3	$78.85	11.433%	$87.8649	$87.86	$87.85	$87.90
Purchase #4	$27.46	8.853%	$29.891	$29.89	$29.90	$29.90
Purchase #5	$237.73	12.368%	$267.1324	$267.13	$267.15	$267.10
Purchase #6	$60.34	4.585%	$63.1066	$63.11	$63.10	$63.10
Purchase #7	$173.26	10.766%	$191.9132	$191.91	$191.90	$191.90
7 purchase totals =	$798.89		$877.3820	$877.38	$877.40	$877.30