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	$50.27	10.231%	$55.4131	$55.41	$55.40	$55.40
Purchase #2	$209.38	4.297%	$218.3771	$218.38	$218.40	$218.40
Purchase #3	$159.31	3.517%	$164.9129	$164.91	$164.90	$164.90
Purchase #4	$191.53	7.175%	$205.2723	$205.27	$205.25	$205.30
Purchase #5	$96.66	11.803%	$108.0688	$108.07	$108.05	$108.10
Purchase #6	$228.99	9.341%	$250.38	$250.38	$250.40	$250.40
Purchase #7	$70.54	10.457%	$77.9164	$77.92	$77.90	$77.90
7 purchase totals =	$1,006.68		$1,080.3406	$1,080.34	$1,080.30	$1,080.40