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	$234.52	11.539%	$261.5813	$261.58	$261.60	$261.60
Purchase #2	$78.32	3.285%	$80.8928	$80.89	$80.90	$80.90
Purchase #3	$86.88	11.111%	$96.5332	$96.53	$96.55	$96.50
Purchase #4	$197.35	4.112%	$205.465	$205.47	$205.45	$205.50
Purchase #5	$200.66	8.708%	$218.1335	$218.13	$218.15	$218.10
Purchase #6	$155.98	5.205%	$164.0988	$164.10	$164.10	$164.10
Purchase #7	$35.69	11.217%	$39.6933	$39.69	$39.70	$39.70
7 purchase totals =	$989.40		$1,066.3979	$1,066.39	$1,066.45	$1,066.40