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	$86.33	11.653%	$96.39	$96.39	$96.40	$96.40
Purchase #2	$120.71	3.824%	$125.326	$125.33	$125.35	$125.30
Purchase #3	$120.43	8.443%	$130.5979	$130.60	$130.60	$130.60
Purchase #4	$216.26	8.726%	$235.1308	$235.13	$235.15	$235.10
Purchase #5	$41.87	3.251%	$43.2312	$43.23	$43.25	$43.20
Purchase #6	$69.67	13.267%	$78.9131	$78.91	$78.90	$78.90
Purchase #7	$145.42	3.459%	$150.4501	$150.45	$150.45	$150.50
7 purchase totals =	$800.69		$860.0391	$860.04	$860.10	$860.00