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	$170.65	5.799%	$180.546	$180.55	$180.55	$180.50
Purchase #2	$87.99	9.639%	$96.4714	$96.47	$96.45	$96.50
Purchase #3	$101.58	7.189%	$108.8826	$108.88	$108.90	$108.90
Purchase #4	$135.59	4.367%	$141.5112	$141.51	$141.50	$141.50
Purchase #5	$98.35	3.112%	$101.4107	$101.41	$101.40	$101.40
Purchase #6	$144.78	10.409%	$159.8502	$159.85	$159.85	$159.90
Purchase #7	$223.64	3.322%	$231.0693	$231.07	$231.05	$231.10
7 purchase totals =	$962.58		$1,019.7414	$1,019.74	$1,019.70	$1,019.80