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	$26.36	7.749%	$28.4026	$28.40	$28.40	$28.40
Purchase #2	$23.74	9.217%	$25.9281	$25.93	$25.95	$25.90
Purchase #3	$36.33	5.268%	$38.2439	$38.24	$38.25	$38.20
Purchase #4	$231.73	6.650%	$247.14	$247.14	$247.15	$247.10
Purchase #5	$31.31	5.221%	$32.9447	$32.94	$32.95	$32.90
Purchase #6	$64.90	11.617%	$72.4394	$72.44	$72.45	$72.40
Purchase #7	$36.69	4.180%	$38.2236	$38.22	$38.20	$38.20
7 purchase totals =	$451.06		$483.3223	$483.31	$483.35	$483.10