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	$10.38	10.188%	$11.4375	$11.44	$11.45	$11.40
Purchase #2	$72.33	8.621%	$78.5656	$78.57	$78.55	$78.60
Purchase #3	$189.76	9.864%	$208.4779	$208.48	$208.50	$208.50
Purchase #4	$85.87	4.486%	$89.7221	$89.72	$89.70	$89.70
Purchase #5	$178.54	7.424%	$191.7948	$191.79	$191.80	$191.80
Purchase #6	$74.80	11.369%	$83.304	$83.30	$83.30	$83.30
Purchase #7	$95.75	5.463%	$100.9808	$100.98	$101.00	$101.00
7 purchase totals =	$707.43		$764.2827	$764.28	$764.30	$764.30