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	$150.58	13.847%	$171.4308	$171.43	$171.45	$171.40
Purchase #2	$225.76	13.192%	$255.5423	$255.54	$255.55	$255.50
Purchase #3	$231.89	13.616%	$263.4641	$263.46	$263.45	$263.50
Purchase #4	$35.33	8.102%	$38.1924	$38.19	$38.20	$38.20
Purchase #5	$111.78	3.165%	$115.3178	$115.32	$115.30	$115.30
Purchase #6	$148.78	5.729%	$157.3036	$157.30	$157.30	$157.30
Purchase #7	$151.62	6.651%	$161.7042	$161.70	$161.70	$161.70
7 purchase totals =	$1,055.74		$1,162.9552	$1,162.94	$1,162.95	$1,162.90