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	$191.89	10.724%	$212.4683	$212.47	$212.45	$212.50
Purchase #2	$175.68	9.234%	$191.9023	$191.90	$191.90	$191.90
Purchase #3	$65.77	10.294%	$72.5404	$72.54	$72.55	$72.50
Purchase #4	$117.99	12.121%	$132.2916	$132.29	$132.30	$132.30
Purchase #5	$215.91	7.624%	$232.371	$232.37	$232.35	$232.40
Purchase #6	$115.52	13.245%	$130.8206	$130.82	$130.80	$130.80
Purchase #7	$95.48	4.623%	$99.894	$99.89	$99.90	$99.90
7 purchase totals =	$978.24		$1,072.2882	$1,072.28	$1,072.25	$1,072.30