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	$48.97	12.439%	$55.0614	$55.06	$55.05	$55.10
Purchase #2	$117.59	12.694%	$132.5169	$132.52	$132.50	$132.50
Purchase #3	$166.71	3.498%	$172.5415	$172.54	$172.55	$172.50
Purchase #4	$210.37	5.383%	$221.6942	$221.69	$221.70	$221.70
Purchase #5	$72.83	3.132%	$75.111	$75.11	$75.10	$75.10
Purchase #6	$94.55	11.868%	$105.7712	$105.77	$105.75	$105.80
Purchase #7	$99.29	13.442%	$112.6366	$112.64	$112.65	$112.60
7 purchase totals =	$810.31		$875.3328	$875.33	$875.30	$875.30