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	$222.31	11.383%	$247.6155	$247.62	$247.60	$247.60
Purchase #2	$168.68	12.835%	$190.3301	$190.33	$190.35	$190.30
Purchase #3	$35.79	6.796%	$38.2223	$38.22	$38.20	$38.20
Purchase #4	$120.71	8.816%	$131.3518	$131.35	$131.35	$131.40
Purchase #5	$67.76	5.667%	$71.6	$71.60	$71.60	$71.60
Purchase #6	$80.62	13.609%	$91.5916	$91.59	$91.60	$91.60
Purchase #7	$239.73	12.509%	$269.7178	$269.72	$269.70	$269.70
7 purchase totals =	$935.60		$1,040.4291	$1,040.43	$1,040.40	$1,040.40