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	$166.29	11.712%	$185.7659	$185.77	$185.75	$185.80
Purchase #2	$64.68	11.610%	$72.1893	$72.19	$72.20	$72.20
Purchase #3	$182.58	6.813%	$195.0192	$195.02	$195.00	$195.00
Purchase #4	$144.91	5.854%	$153.393	$153.39	$153.40	$153.40
Purchase #5	$95.46	3.658%	$98.9519	$98.95	$98.95	$99.00
Purchase #6	$102.32	6.558%	$109.0301	$109.03	$109.05	$109.00
Purchase #7	$82.47	3.718%	$85.5362	$85.54	$85.55	$85.50
7 purchase totals =	$838.71		$899.8856	$899.89	$899.90	$899.90