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	$10.58	3.120%	$10.9101	$10.91	$10.90	$10.90
Purchase #2	$24.68	11.302%	$27.4693	$27.47	$27.45	$27.50
Purchase #3	$53.64	13.864%	$61.0766	$61.08	$61.10	$61.10
Purchase #4	$130.51	3.280%	$134.7907	$134.79	$134.80	$134.80
Purchase #5	$207.32	13.536%	$235.3828	$235.38	$235.40	$235.40
Purchase #6	$172.61	7.655%	$185.8233	$185.82	$185.80	$185.80
Purchase #7	$74.86	5.360%	$78.8725	$78.87	$78.85	$78.90
7 purchase totals =	$674.20		$734.3253	$734.32	$734.30	$734.40