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	$58.71	11.205%	$65.2885	$65.29	$65.30	$65.30
Purchase #2	$74.88	4.597%	$78.3222	$78.32	$78.30	$78.30
Purchase #3	$109.87	4.297%	$114.5911	$114.59	$114.60	$114.60
Purchase #4	$131.67	3.700%	$136.5418	$136.54	$136.55	$136.50
Purchase #5	$225.76	7.359%	$242.3737	$242.37	$242.35	$242.40
Purchase #6	$60.80	9.211%	$66.4003	$66.40	$66.40	$66.40
Purchase #7	$207.91	12.440%	$233.774	$233.77	$233.75	$233.80
7 purchase totals =	$869.60		$937.2916	$937.28	$937.25	$937.30