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	$105.87	3.869%	$109.9661	$109.97	$109.95	$110.00
Purchase #2	$108.95	13.751%	$123.9317	$123.93	$123.95	$123.90
Purchase #3	$50.36	8.279%	$54.5293	$54.53	$54.55	$54.50
Purchase #4	$60.34	3.728%	$62.5895	$62.59	$62.60	$62.60
Purchase #5	$232.94	6.289%	$247.5896	$247.59	$247.60	$247.60
Purchase #6	$162.75	3.500%	$168.4463	$168.45	$168.45	$168.40
Purchase #7	$44.95	12.853%	$50.7274	$50.73	$50.75	$50.70
7 purchase totals =	$766.16		$817.7799	$817.79	$817.85	$817.70