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	$69.87	6.553%	$74.4486	$74.45	$74.45	$74.40
Purchase #2	$172.49	9.444%	$188.78	$188.78	$188.80	$188.80
Purchase #3	$19.53	8.219%	$21.1352	$21.14	$21.15	$21.10
Purchase #4	$71.26	10.507%	$78.7473	$78.75	$78.75	$78.70
Purchase #5	$191.60	9.331%	$209.4782	$209.48	$209.50	$209.50
Purchase #6	$106.25	3.444%	$109.9093	$109.91	$109.90	$109.90
Purchase #7	$49.64	11.711%	$55.4533	$55.45	$55.45	$55.50
7 purchase totals =	$680.64		$737.9519	$737.96	$738.00	$737.90