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	$137.59	10.264%	$151.7122	$151.71	$151.70	$151.70
Purchase #2	$186.96	5.254%	$196.7829	$196.78	$196.80	$196.80
Purchase #3	$47.86	7.592%	$51.4935	$51.49	$51.50	$51.50
Purchase #4	$73.28	7.340%	$78.6588	$78.66	$78.65	$78.70
Purchase #5	$186.84	11.845%	$208.9712	$208.97	$208.95	$209.00
Purchase #6	$220.63	13.566%	$250.5607	$250.56	$250.55	$250.60
Purchase #7	$87.77	6.168%	$93.1837	$93.18	$93.20	$93.20
7 purchase totals =	$940.93		$1,031.3630	$1,031.35	$1,031.35	$1,031.50