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	$107.30	3.586%	$111.1478	$111.15	$111.15	$111.10
Purchase #2	$59.56	3.410%	$61.591	$61.59	$61.60	$61.60
Purchase #3	$209.70	13.463%	$237.9319	$237.93	$237.95	$237.90
Purchase #4	$124.62	3.187%	$128.5916	$128.59	$128.60	$128.60
Purchase #5	$134.71	5.398%	$141.9816	$141.98	$142.00	$142.00
Purchase #6	$165.70	3.663%	$171.7696	$171.77	$171.75	$171.80
Purchase #7	$8.40	5.856%	$8.8919	$8.89	$8.90	$8.90
7 purchase totals =	$809.99		$861.9054	$861.90	$861.95	$861.90