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	$190.93	3.318%	$197.2651	$197.27	$197.25	$197.30
Purchase #2	$232.27	4.309%	$242.2785	$242.28	$242.30	$242.30
Purchase #3	$239.50	4.196%	$249.5494	$249.55	$249.55	$249.50
Purchase #4	$117.35	12.139%	$131.5951	$131.60	$131.60	$131.60
Purchase #5	$143.80	4.680%	$150.5298	$150.53	$150.55	$150.50
Purchase #6	$93.69	12.738%	$105.6242	$105.62	$105.60	$105.60
Purchase #7	$105.73	6.151%	$112.2335	$112.23	$112.25	$112.20
7 purchase totals =	$1,123.27		$1,189.0756	$1,189.08	$1,189.10	$1,189.00