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	$188.27	6.688%	$200.8615	$200.86	$200.85	$200.90
Purchase #2	$187.59	11.230%	$208.6564	$208.66	$208.65	$208.70
Purchase #3	$35.87	6.117%	$38.0642	$38.06	$38.05	$38.10
Purchase #4	$6.83	6.738%	$7.2902	$7.29	$7.30	$7.30
Purchase #5	$126.99	6.160%	$134.8126	$134.81	$134.80	$134.80
Purchase #6	$81.30	10.803%	$90.0828	$90.08	$90.10	$90.10
Purchase #7	$126.70	3.279%	$130.8545	$130.85	$130.85	$130.90
7 purchase totals =	$753.55		$810.6222	$810.61	$810.60	$810.80