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	$162.27	3.237%	$167.5227	$167.52	$167.50	$167.50
Purchase #2	$41.28	4.707%	$43.223	$43.22	$43.20	$43.20
Purchase #3	$173.63	6.872%	$185.5619	$185.56	$185.55	$185.60
Purchase #4	$130.96	8.831%	$142.5251	$142.53	$142.55	$142.50
Purchase #5	$195.73	5.248%	$206.0019	$206.00	$206.00	$206.00
Purchase #6	$113.37	6.870%	$121.1585	$121.16	$121.15	$121.20
Purchase #7	$128.31	11.865%	$143.534	$143.53	$143.55	$143.50
7 purchase totals =	$945.55		$1,009.5271	$1,009.52	$1,009.50	$1,009.50