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	$132.89	7.311%	$142.6056	$142.61	$142.60	$142.60
Purchase #2	$44.45	4.827%	$46.5956	$46.60	$46.60	$46.60
Purchase #3	$146.99	6.354%	$156.3297	$156.33	$156.35	$156.30
Purchase #4	$22.96	12.799%	$25.8987	$25.90	$25.90	$25.90
Purchase #5	$216.56	3.112%	$223.2993	$223.30	$223.30	$223.30
Purchase #6	$35.37	6.816%	$37.7808	$37.78	$37.80	$37.80
Purchase #7	$41.33	6.300%	$43.9338	$43.93	$43.95	$43.90
7 purchase totals =	$640.55		$676.4435	$676.45	$676.50	$676.40