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	$120.59	6.218%	$128.0883	$128.09	$128.10	$128.10
Purchase #2	$139.87	5.304%	$147.2887	$147.29	$147.30	$147.30
Purchase #3	$249.87	10.239%	$275.4542	$275.45	$275.45	$275.50
Purchase #4	$35.32	13.575%	$40.1147	$40.11	$40.10	$40.10
Purchase #5	$179.85	5.843%	$190.3586	$190.36	$190.35	$190.40
Purchase #6	$161.92	3.674%	$167.8689	$167.87	$167.85	$167.90
Purchase #7	$164.61	12.721%	$185.55	$185.55	$185.55	$185.60
7 purchase totals =	$1,052.03		$1,134.7234	$1,134.72	$1,134.70	$1,134.90