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	$56.97	5.352%	$60.019	$60.02	$60.00	$60.00
Purchase #2	$25.78	9.807%	$28.3082	$28.31	$28.30	$28.30
Purchase #3	$77.77	10.337%	$85.8091	$85.81	$85.80	$85.80
Purchase #4	$50.97	7.740%	$54.9151	$54.92	$54.90	$54.90
Purchase #5	$18.93	10.373%	$20.8936	$20.89	$20.90	$20.90
Purchase #6	$186.68	5.344%	$196.6562	$196.66	$196.65	$196.70
Purchase #7	$119.64	7.655%	$128.7984	$128.80	$128.80	$128.80
7 purchase totals =	$536.74		$575.3996	$575.41	$575.35	$575.40