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	$56.87	5.238%	$59.8489	$59.85	$59.85	$59.80
Purchase #2	$25.32	12.763%	$28.5516	$28.55	$28.55	$28.60
Purchase #3	$79.73	11.426%	$88.8399	$88.84	$88.85	$88.80
Purchase #4	$241.67	3.498%	$250.1236	$250.12	$250.10	$250.10
Purchase #5	$107.92	5.265%	$113.602	$113.60	$113.60	$113.60
Purchase #6	$152.47	6.426%	$162.2677	$162.27	$162.25	$162.30
Purchase #7	$240.99	13.275%	$272.9814	$272.98	$273.00	$273.00
7 purchase totals =	$904.97		$976.2151	$976.21	$976.20	$976.20