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	$111.92	11.469%	$124.7561	$124.76	$124.75	$124.80
Purchase #2	$126.57	11.187%	$140.7294	$140.73	$140.75	$140.70
Purchase #3	$79.98	12.502%	$89.9791	$89.98	$90.00	$90.00
Purchase #4	$75.75	8.611%	$82.2728	$82.27	$82.25	$82.30
Purchase #5	$138.56	13.198%	$156.8471	$156.85	$156.85	$156.80
Purchase #6	$186.80	12.759%	$210.6338	$210.63	$210.65	$210.60
Purchase #7	$200.27	3.254%	$206.7868	$206.79	$206.80	$206.80
7 purchase totals =	$919.85		$1,012.0051	$1,012.01	$1,012.05	$1,012.00