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	$50.95	10.331%	$56.2136	$56.21	$56.20	$56.20
Purchase #2	$121.79	4.185%	$126.8869	$126.89	$126.90	$126.90
Purchase #3	$197.54	6.397%	$210.1766	$210.18	$210.20	$210.20
Purchase #4	$50.43	9.690%	$55.3167	$55.32	$55.30	$55.30
Purchase #5	$194.39	6.231%	$206.5024	$206.50	$206.50	$206.50
Purchase #6	$59.89	12.277%	$67.2427	$67.24	$67.25	$67.20
Purchase #7	$62.41	5.693%	$65.963	$65.96	$65.95	$66.00
7 purchase totals =	$737.40		$788.3019	$788.30	$788.30	$788.30