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	$79.76	4.630%	$83.4529	$83.45	$83.45	$83.50
Purchase #2	$152.60	9.277%	$166.7567	$166.76	$166.75	$166.80
Purchase #3	$181.28	6.526%	$193.1103	$193.11	$193.10	$193.10
Purchase #4	$83.33	6.864%	$89.0498	$89.05	$89.05	$89.00
Purchase #5	$49.70	4.471%	$51.9221	$51.92	$51.90	$51.90
Purchase #6	$106.77	5.330%	$112.4608	$112.46	$112.45	$112.50
Purchase #7	$55.45	3.867%	$57.5943	$57.59	$57.60	$57.60
7 purchase totals =	$708.89		$754.3469	$754.34	$754.30	$754.40