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	$116.75	6.706%	$124.5793	$124.58	$124.60	$124.60
Purchase #2	$101.93	3.641%	$105.6413	$105.64	$105.65	$105.60
Purchase #3	$149.56	5.175%	$157.2997	$157.30	$157.30	$157.30
Purchase #4	$90.81	9.805%	$99.7139	$99.71	$99.70	$99.70
Purchase #5	$191.90	9.179%	$209.5145	$209.51	$209.50	$209.50
Purchase #6	$99.26	4.364%	$103.5917	$103.59	$103.60	$103.60
Purchase #7	$118.43	6.166%	$125.7324	$125.73	$125.75	$125.70
7 purchase totals =	$868.64		$926.0728	$926.06	$926.10	$926.00