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	$121.72	4.547%	$127.2546	$127.25	$127.25	$127.30
Purchase #2	$95.54	8.721%	$103.872	$103.87	$103.85	$103.90
Purchase #3	$44.53	8.510%	$48.3195	$48.32	$48.30	$48.30
Purchase #4	$57.57	8.802%	$62.6373	$62.64	$62.65	$62.60
Purchase #5	$48.27	7.540%	$51.9096	$51.91	$51.90	$51.90
Purchase #6	$67.66	9.696%	$74.2203	$74.22	$74.20	$74.20
Purchase #7	$218.65	5.708%	$231.1305	$231.13	$231.15	$231.10
7 purchase totals =	$653.94		$699.3438	$699.34	$699.30	$699.30