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	$175.91	3.730%	$182.4714	$182.47	$182.45	$182.50
Purchase #2	$174.91	12.102%	$196.0776	$196.08	$196.10	$196.10
Purchase #3	$49.50	12.149%	$55.5138	$55.51	$55.50	$55.50
Purchase #4	$182.53	12.420%	$205.2002	$205.20	$205.20	$205.20
Purchase #5	$103.98	5.223%	$109.4109	$109.41	$109.40	$109.40
Purchase #6	$149.56	12.187%	$167.7869	$167.79	$167.80	$167.80
Purchase #7	$160.83	12.175%	$180.4111	$180.41	$180.40	$180.40
7 purchase totals =	$997.22		$1,096.8719	$1,096.87	$1,096.85	$1,096.90