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	$122.60	7.616%	$131.9372	$131.94	$131.95	$131.90
Purchase #2	$146.58	4.558%	$153.2611	$153.26	$153.25	$153.30
Purchase #3	$131.36	11.495%	$146.4598	$146.46	$146.45	$146.50
Purchase #4	$107.54	3.776%	$111.6007	$111.60	$111.60	$111.60
Purchase #5	$240.76	4.108%	$250.6504	$250.65	$250.65	$250.70
Purchase #6	$242.58	10.352%	$267.6919	$267.69	$267.70	$267.70
Purchase #7	$183.32	13.229%	$207.5714	$207.57	$207.55	$207.60
7 purchase totals =	$1,174.74		$1,269.1725	$1,269.17	$1,269.15	$1,269.30