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	$42.39	6.865%	$45.3001	$45.30	$45.30	$45.30
Purchase #2	$162.25	3.596%	$168.0845	$168.08	$168.10	$168.10
Purchase #3	$215.89	9.362%	$236.1016	$236.10	$236.10	$236.10
Purchase #4	$119.95	6.387%	$127.6112	$127.61	$127.60	$127.60
Purchase #5	$209.75	6.710%	$223.8242	$223.82	$223.80	$223.80
Purchase #6	$205.49	6.589%	$219.0297	$219.03	$219.05	$219.00
Purchase #7	$199.91	8.485%	$216.8724	$216.87	$216.85	$216.90
7 purchase totals =	$1,155.63		$1,236.8237	$1,236.81	$1,236.80	$1,236.80