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	$8.89	5.274%	$9.3589	$9.36	$9.35	$9.40
Purchase #2	$67.26	8.486%	$72.9677	$72.97	$72.95	$73.00
Purchase #3	$17.72	3.137%	$18.2759	$18.28	$18.30	$18.30
Purchase #4	$81.42	4.550%	$85.1246	$85.12	$85.10	$85.10
Purchase #5	$127.43	13.505%	$144.6394	$144.64	$144.65	$144.60
Purchase #6	$210.35	10.251%	$231.913	$231.91	$231.90	$231.90
Purchase #7	$216.94	4.839%	$227.4377	$227.44	$227.45	$227.40
7 purchase totals =	$730.01		$789.7172	$789.72	$789.70	$789.70