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	$163.48	10.452%	$180.5669	$180.57	$180.55	$180.60
Purchase #2	$167.87	8.317%	$181.8317	$181.83	$181.85	$181.80
Purchase #3	$236.56	7.323%	$253.8833	$253.88	$253.90	$253.90
Purchase #4	$113.46	12.260%	$127.3702	$127.37	$127.35	$127.40
Purchase #5	$117.73	9.484%	$128.8955	$128.90	$128.90	$128.90
Purchase #6	$26.34	5.757%	$27.8564	$27.86	$27.85	$27.90
Purchase #7	$41.87	10.829%	$46.4041	$46.40	$46.40	$46.40
7 purchase totals =	$867.31		$946.8081	$946.81	$946.80	$946.90