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	$221.38	9.718%	$242.8937	$242.89	$242.90	$242.90
Purchase #2	$144.49	12.643%	$162.7579	$162.76	$162.75	$162.80
Purchase #3	$173.86	6.622%	$185.373	$185.37	$185.35	$185.40
Purchase #4	$52.71	7.721%	$56.7797	$56.78	$56.80	$56.80
Purchase #5	$194.32	11.322%	$216.3209	$216.32	$216.30	$216.30
Purchase #6	$123.28	4.760%	$129.1481	$129.15	$129.15	$129.10
Purchase #7	$113.25	5.529%	$119.5116	$119.51	$119.50	$119.50
7 purchase totals =	$1,023.29		$1,112.7849	$1,112.78	$1,112.75	$1,112.80