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	$58.53	11.226%	$65.1006	$65.10	$65.10	$65.10
Purchase #2	$214.50	4.358%	$223.8479	$223.85	$223.85	$223.80
Purchase #3	$99.89	11.521%	$111.3983	$111.40	$111.40	$111.40
Purchase #4	$12.89	3.280%	$13.3128	$13.31	$13.30	$13.30
Purchase #5	$188.89	3.761%	$195.9942	$195.99	$196.00	$196.00
Purchase #6	$68.36	3.570%	$70.8005	$70.80	$70.80	$70.80
Purchase #7	$23.93	13.149%	$27.0766	$27.08	$27.10	$27.10
7 purchase totals =	$666.99		$707.5309	$707.53	$707.55	$707.50