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	$40.91	5.255%	$43.0598	$43.06	$43.05	$43.10
Purchase #2	$129.33	13.686%	$147.0301	$147.03	$147.05	$147.00
Purchase #3	$77.27	11.436%	$86.1066	$86.11	$86.10	$86.10
Purchase #4	$100.78	8.800%	$109.6486	$109.65	$109.65	$109.60
Purchase #5	$160.90	3.452%	$166.4543	$166.45	$166.45	$166.50
Purchase #6	$89.53	7.702%	$96.4256	$96.43	$96.45	$96.40
Purchase #7	$10.56	4.434%	$11.0282	$11.03	$11.05	$11.00
7 purchase totals =	$609.28		$659.7532	$659.76	$659.80	$659.70