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	$173.90	7.450%	$186.8556	$186.86	$186.85	$186.90
Purchase #2	$49.70	9.411%	$54.3773	$54.38	$54.40	$54.40
Purchase #3	$92.60	7.207%	$99.2737	$99.27	$99.25	$99.30
Purchase #4	$162.27	11.199%	$180.4426	$180.44	$180.45	$180.40
Purchase #5	$157.92	11.460%	$176.0176	$176.02	$176.00	$176.00
Purchase #6	$238.66	9.663%	$261.7217	$261.72	$261.70	$261.70
Purchase #7	$51.34	4.845%	$53.8274	$53.83	$53.85	$53.80
7 purchase totals =	$926.39		$1,012.5159	$1,012.52	$1,012.50	$1,012.50