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	$88.42	4.707%	$92.5819	$92.58	$92.60	$92.60
Purchase #2	$222.31	11.765%	$248.4648	$248.46	$248.45	$248.50
Purchase #3	$28.55	9.144%	$31.1606	$31.16	$31.15	$31.20
Purchase #4	$70.45	4.149%	$73.373	$73.37	$73.35	$73.40
Purchase #5	$202.91	10.735%	$224.6924	$224.69	$224.70	$224.70
Purchase #6	$245.86	11.618%	$274.424	$274.42	$274.40	$274.40
Purchase #7	$75.35	4.735%	$78.9178	$78.92	$78.90	$78.90
7 purchase totals =	$933.85		$1,023.6145	$1,023.60	$1,023.55	$1,023.70