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	$173.90	12.866%	$196.274	$196.27	$196.25	$196.30
Purchase #2	$248.89	8.593%	$270.2771	$270.28	$270.30	$270.30
Purchase #3	$119.84	3.440%	$123.9625	$123.96	$123.95	$124.00
Purchase #4	$140.69	9.813%	$154.4959	$154.50	$154.50	$154.50
Purchase #5	$41.59	3.165%	$42.9063	$42.91	$42.90	$42.90
Purchase #6	$180.68	5.124%	$189.938	$189.94	$189.95	$189.90
Purchase #7	$24.54	13.760%	$27.9167	$27.92	$27.90	$27.90
7 purchase totals =	$930.13		$1,005.7705	$1,005.78	$1,005.75	$1,005.80