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	$117.50	11.112%	$130.5566	$130.56	$130.55	$130.60
Purchase #2	$59.91	9.199%	$65.4211	$65.42	$65.40	$65.40
Purchase #3	$205.91	12.359%	$231.3584	$231.36	$231.35	$231.40
Purchase #4	$99.64	12.148%	$111.7443	$111.74	$111.75	$111.70
Purchase #5	$236.73	5.583%	$249.9466	$249.95	$249.95	$249.90
Purchase #6	$90.94	4.484%	$95.0177	$95.02	$95.00	$95.00
Purchase #7	$94.27	6.334%	$100.2411	$100.24	$100.25	$100.20
7 purchase totals =	$904.90		$984.2858	$984.29	$984.25	$984.20