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	$183.49	6.305%	$195.059	$195.06	$195.05	$195.10
Purchase #2	$131.69	12.228%	$147.7931	$147.79	$147.80	$147.80
Purchase #3	$33.90	11.538%	$37.8114	$37.81	$37.80	$37.80
Purchase #4	$170.90	6.418%	$181.8684	$181.87	$181.85	$181.90
Purchase #5	$144.44	8.394%	$156.5643	$156.56	$156.55	$156.60
Purchase #6	$105.78	11.785%	$118.2462	$118.25	$118.25	$118.20
Purchase #7	$200.65	9.218%	$219.1459	$219.15	$219.15	$219.10
7 purchase totals =	$970.85		$1,056.4883	$1,056.49	$1,056.45	$1,056.50