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	$40.49	13.206%	$45.8371	$45.84	$45.85	$45.80
Purchase #2	$22.38	6.612%	$23.8598	$23.86	$23.85	$23.90
Purchase #3	$102.95	12.150%	$115.4584	$115.46	$115.45	$115.50
Purchase #4	$198.27	9.210%	$216.5307	$216.53	$216.55	$216.50
Purchase #5	$231.30	5.386%	$243.7578	$243.76	$243.75	$243.80
Purchase #6	$87.47	3.507%	$90.5376	$90.54	$90.55	$90.50
Purchase #7	$36.89	11.582%	$41.1626	$41.16	$41.15	$41.20
7 purchase totals =	$719.75		$777.1440	$777.15	$777.15	$777.20