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	$113.53	12.540%	$127.7667	$127.77	$127.75	$127.80
Purchase #2	$25.95	4.369%	$27.0838	$27.08	$27.10	$27.10
Purchase #3	$166.54	11.617%	$185.887	$185.89	$185.90	$185.90
Purchase #4	$191.89	6.244%	$203.8716	$203.87	$203.85	$203.90
Purchase #5	$249.54	9.533%	$273.3286	$273.33	$273.35	$273.30
Purchase #6	$87.53	11.367%	$97.4795	$97.48	$97.50	$97.50
Purchase #7	$138.85	8.128%	$150.1357	$150.14	$150.15	$150.10
7 purchase totals =	$973.83		$1,065.5529	$1,065.56	$1,065.60	$1,065.60