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	$166.61	4.489%	$174.0891	$174.09	$174.10	$174.10
Purchase #2	$84.56	7.792%	$91.1489	$91.15	$91.15	$91.10
Purchase #3	$31.47	4.782%	$32.9749	$32.97	$32.95	$33.00
Purchase #4	$80.78	11.303%	$89.9106	$89.91	$89.90	$89.90
Purchase #5	$99.81	8.742%	$108.5354	$108.54	$108.55	$108.50
Purchase #6	$228.60	9.278%	$249.8095	$249.81	$249.80	$249.80
Purchase #7	$113.51	12.344%	$127.5217	$127.52	$127.50	$127.50
7 purchase totals =	$805.34		$873.9901	$873.99	$873.95	$873.90