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	$224.67	10.813%	$248.9636	$248.96	$248.95	$249.00
Purchase #2	$167.90	8.418%	$182.0338	$182.03	$182.05	$182.00
Purchase #3	$238.54	7.148%	$255.5908	$255.59	$255.60	$255.60
Purchase #4	$176.36	11.639%	$196.8865	$196.89	$196.90	$196.90
Purchase #5	$87.95	5.618%	$92.891	$92.89	$92.90	$92.90
Purchase #6	$38.28	6.651%	$40.826	$40.83	$40.85	$40.80
Purchase #7	$28.34	9.793%	$31.1153	$31.12	$31.10	$31.10
7 purchase totals =	$962.04		$1,048.3070	$1,048.31	$1,048.35	$1,048.30