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	$96.52	8.432%	$104.6586	$104.66	$104.65	$104.70
Purchase #2	$233.54	10.135%	$257.2093	$257.21	$257.20	$257.20
Purchase #3	$21.48	5.870%	$22.7409	$22.74	$22.75	$22.70
Purchase #4	$126.38	10.199%	$139.2695	$139.27	$139.25	$139.30
Purchase #5	$112.50	13.187%	$127.3354	$127.34	$127.35	$127.30
Purchase #6	$42.93	5.474%	$45.28	$45.28	$45.30	$45.30
Purchase #7	$98.39	11.307%	$109.515	$109.52	$109.50	$109.50
7 purchase totals =	$731.74		$806.0087	$806.02	$806.00	$806.00