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	$112.33	5.356%	$118.3464	$118.35	$118.35	$118.30
Purchase #2	$97.25	10.282%	$107.2492	$107.25	$107.25	$107.20
Purchase #3	$225.82	10.544%	$249.6305	$249.63	$249.65	$249.60
Purchase #4	$154.52	11.331%	$172.0287	$172.03	$172.05	$172.00
Purchase #5	$232.95	7.464%	$250.3374	$250.34	$250.35	$250.30
Purchase #6	$29.93	4.346%	$31.2308	$31.23	$31.25	$31.20
Purchase #7	$170.82	6.818%	$182.4665	$182.47	$182.45	$182.50
7 purchase totals =	$1,023.62		$1,111.2895	$1,111.30	$1,111.35	$1,111.10