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	$101.49	7.720%	$109.325	$109.33	$109.35	$109.30
Purchase #2	$227.72	4.733%	$238.498	$238.50	$238.50	$238.50
Purchase #3	$62.30	8.836%	$67.8048	$67.80	$67.80	$67.80
Purchase #4	$220.31	10.163%	$242.7001	$242.70	$242.70	$242.70
Purchase #5	$99.72	3.355%	$103.0656	$103.07	$103.05	$103.10
Purchase #6	$219.48	9.708%	$240.7871	$240.79	$240.80	$240.80
Purchase #7	$10.73	10.688%	$11.8768	$11.88	$11.90	$11.90
7 purchase totals =	$941.75		$1,014.0574	$1,014.07	$1,014.10	$1,014.10