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	$99.69	5.795%	$105.467	$105.47	$105.45	$105.50
Purchase #2	$147.74	5.761%	$156.2513	$156.25	$156.25	$156.30
Purchase #3	$30.49	7.353%	$32.7319	$32.73	$32.75	$32.70
Purchase #4	$152.88	5.484%	$161.2639	$161.26	$161.25	$161.30
Purchase #5	$19.50	4.308%	$20.3401	$20.34	$20.35	$20.30
Purchase #6	$174.40	7.598%	$187.6509	$187.65	$187.65	$187.70
Purchase #7	$32.86	9.222%	$35.8903	$35.89	$35.90	$35.90
7 purchase totals =	$657.56		$699.5954	$699.59	$699.60	$699.70