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	$148.65	6.614%	$158.4817	$158.48	$158.50	$158.50
Purchase #2	$65.39	3.328%	$67.5662	$67.57	$67.55	$67.60
Purchase #3	$147.83	3.139%	$152.4704	$152.47	$152.45	$152.50
Purchase #4	$59.45	6.394%	$63.2512	$63.25	$63.25	$63.30
Purchase #5	$86.31	4.200%	$89.935	$89.94	$89.95	$89.90
Purchase #6	$243.40	9.606%	$266.781	$266.78	$266.80	$266.80
Purchase #7	$48.91	3.773%	$50.7554	$50.76	$50.75	$50.80
7 purchase totals =	$799.94		$849.2409	$849.25	$849.25	$849.40