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	$43.48	9.391%	$47.5632	$47.56	$47.55	$47.60
Purchase #2	$239.91	10.406%	$264.875	$264.88	$264.90	$264.90
Purchase #3	$82.27	4.752%	$86.1795	$86.18	$86.20	$86.20
Purchase #4	$85.64	11.546%	$95.528	$95.53	$95.55	$95.50
Purchase #5	$209.64	5.499%	$221.1681	$221.17	$221.15	$221.20
Purchase #6	$145.69	3.275%	$150.4613	$150.46	$150.45	$150.50
Purchase #7	$119.70	9.840%	$131.4785	$131.48	$131.50	$131.50
7 purchase totals =	$926.33		$997.2536	$997.26	$997.30	$997.40