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	$93.36	11.831%	$104.4054	$104.41	$104.40	$104.40
Purchase #2	$12.30	7.120%	$13.1758	$13.18	$13.20	$13.20
Purchase #3	$217.69	4.742%	$228.0129	$228.01	$228.00	$228.00
Purchase #4	$86.32	4.625%	$90.3123	$90.31	$90.30	$90.30
Purchase #5	$187.37	4.407%	$195.6274	$195.63	$195.65	$195.60
Purchase #6	$79.61	12.834%	$89.8271	$89.83	$89.85	$89.80
Purchase #7	$183.83	6.837%	$196.3985	$196.40	$196.40	$196.40
7 purchase totals =	$860.48		$917.7594	$917.77	$917.80	$917.70