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	$160.39	9.296%	$175.2999	$175.30	$175.30	$175.30
Purchase #2	$159.51	6.493%	$169.867	$169.87	$169.85	$169.90
Purchase #3	$155.92	10.665%	$172.5489	$172.55	$172.55	$172.50
Purchase #4	$7.55	9.596%	$8.2745	$8.27	$8.25	$8.30
Purchase #5	$218.38	6.805%	$233.2408	$233.24	$233.25	$233.20
Purchase #6	$148.89	6.299%	$158.2686	$158.27	$158.25	$158.30
Purchase #7	$47.94	9.152%	$52.3275	$52.33	$52.35	$52.30
7 purchase totals =	$898.58		$969.8272	$969.83	$969.80	$969.80