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	$39.75	4.335%	$41.4732	$41.47	$41.45	$41.50
Purchase #2	$72.89	13.315%	$82.5953	$82.60	$82.60	$82.60
Purchase #3	$101.27	12.191%	$113.6158	$113.62	$113.60	$113.60
Purchase #4	$114.48	4.212%	$119.3019	$119.30	$119.30	$119.30
Purchase #5	$248.84	6.376%	$264.706	$264.71	$264.70	$264.70
Purchase #6	$220.37	13.150%	$249.3487	$249.35	$249.35	$249.30
Purchase #7	$50.94	10.487%	$56.2821	$56.28	$56.30	$56.30
7 purchase totals =	$848.54		$927.3230	$927.33	$927.30	$927.30