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	$133.96	5.660%	$141.5421	$141.54	$141.55	$141.50
Purchase #2	$7.67	10.698%	$8.4905	$8.49	$8.50	$8.50
Purchase #3	$164.81	13.790%	$187.5373	$187.54	$187.55	$187.50
Purchase #4	$96.33	13.741%	$109.5667	$109.57	$109.55	$109.60
Purchase #5	$140.91	4.815%	$147.6948	$147.69	$147.70	$147.70
Purchase #6	$57.56	6.219%	$61.1397	$61.14	$61.15	$61.10
Purchase #7	$250.65	3.607%	$259.6909	$259.69	$259.70	$259.70
7 purchase totals =	$851.89		$915.6620	$915.66	$915.70	$915.60