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	$7.71	12.419%	$8.6675	$8.67	$8.65	$8.70
Purchase #2	$117.67	8.559%	$127.7414	$127.74	$127.75	$127.70
Purchase #3	$46.76	8.774%	$50.8627	$50.86	$50.85	$50.90
Purchase #4	$13.50	11.294%	$15.0247	$15.02	$15.00	$15.00
Purchase #5	$39.43	3.615%	$40.8554	$40.86	$40.85	$40.90
Purchase #6	$119.26	3.410%	$123.3268	$123.33	$123.35	$123.30
Purchase #7	$84.41	5.761%	$89.2729	$89.27	$89.25	$89.30
7 purchase totals =	$428.74		$455.7514	$455.75	$455.70	$455.80