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	$163.57	6.326%	$173.9174	$173.92	$173.90	$173.90
Purchase #2	$169.76	3.368%	$175.4775	$175.48	$175.50	$175.50
Purchase #3	$195.59	13.713%	$222.4113	$222.41	$222.40	$222.40
Purchase #4	$144.32	8.842%	$157.0808	$157.08	$157.10	$157.10
Purchase #5	$116.69	9.552%	$127.8362	$127.84	$127.85	$127.80
Purchase #6	$148.59	8.200%	$160.7744	$160.77	$160.75	$160.80
Purchase #7	$89.98	5.368%	$94.8101	$94.81	$94.80	$94.80
7 purchase totals =	$1,028.50		$1,112.3077	$1,112.31	$1,112.30	$1,112.30