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	$162.59	10.651%	$179.9075	$179.91	$179.90	$179.90
Purchase #2	$25.66	6.467%	$27.3194	$27.32	$27.30	$27.30
Purchase #3	$44.33	13.541%	$50.3327	$50.33	$50.35	$50.30
Purchase #4	$81.87	5.527%	$86.395	$86.40	$86.40	$86.40
Purchase #5	$194.44	8.144%	$210.2752	$210.28	$210.30	$210.30
Purchase #6	$59.41	7.657%	$63.959	$63.96	$63.95	$64.00
Purchase #7	$81.30	10.836%	$90.1097	$90.11	$90.10	$90.10
7 purchase totals =	$649.60		$708.2985	$708.31	$708.30	$708.30