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	$44.54	4.718%	$46.6414	$46.64	$46.65	$46.60
Purchase #2	$42.31	7.538%	$45.4993	$45.50	$45.50	$45.50
Purchase #3	$172.79	7.263%	$185.3397	$185.34	$185.35	$185.30
Purchase #4	$107.43	7.846%	$115.859	$115.86	$115.85	$115.90
Purchase #5	$45.48	12.152%	$51.0067	$51.01	$51.00	$51.00
Purchase #6	$122.50	3.652%	$126.9737	$126.97	$126.95	$127.00
Purchase #7	$205.31	11.802%	$229.5407	$229.54	$229.55	$229.50
7 purchase totals =	$740.36		$800.8605	$800.86	$800.85	$800.80