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	$152.80	10.569%	$168.9494	$168.95	$168.95	$168.90
Purchase #2	$161.81	7.738%	$174.3309	$174.33	$174.35	$174.30
Purchase #3	$141.64	3.783%	$146.9982	$147.00	$147.00	$147.00
Purchase #4	$37.60	7.153%	$40.2895	$40.29	$40.30	$40.30
Purchase #5	$40.83	3.627%	$42.3109	$42.31	$42.30	$42.30
Purchase #6	$175.49	4.451%	$183.3011	$183.30	$183.30	$183.30
Purchase #7	$55.53	13.745%	$63.1626	$63.16	$63.15	$63.20
7 purchase totals =	$765.70		$819.3426	$819.34	$819.35	$819.30