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	$93.46	9.215%	$102.0723	$102.07	$102.05	$102.10
Purchase #2	$59.92	11.578%	$66.8575	$66.86	$66.85	$66.90
Purchase #3	$218.31	6.766%	$233.0809	$233.08	$233.10	$233.10
Purchase #4	$53.69	10.385%	$59.2657	$59.27	$59.25	$59.30
Purchase #5	$171.31	3.103%	$176.6257	$176.63	$176.65	$176.60
Purchase #6	$200.31	11.373%	$223.0913	$223.09	$223.10	$223.10
Purchase #7	$31.39	12.256%	$35.2372	$35.24	$35.25	$35.20
7 purchase totals =	$828.39		$896.2306	$896.24	$896.25	$896.30