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	$97.52	5.524%	$102.907	$102.91	$102.90	$102.90
Purchase #2	$133.72	6.652%	$142.6151	$142.62	$142.60	$142.60
Purchase #3	$171.28	4.408%	$178.83	$178.83	$178.85	$178.80
Purchase #4	$149.33	8.863%	$162.5651	$162.57	$162.55	$162.60
Purchase #5	$33.28	8.568%	$36.1314	$36.13	$36.15	$36.10
Purchase #6	$247.76	4.418%	$258.706	$258.71	$258.70	$258.70
Purchase #7	$247.49	3.374%	$255.8403	$255.84	$255.85	$255.80
7 purchase totals =	$1,080.38		$1,137.5949	$1,137.61	$1,137.60	$1,137.50