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	$140.82	8.558%	$152.8714	$152.87	$152.85	$152.90
Purchase #2	$128.52	3.497%	$133.0143	$133.01	$133.00	$133.00
Purchase #3	$67.53	3.649%	$69.9942	$69.99	$70.00	$70.00
Purchase #4	$35.69	4.257%	$37.2093	$37.21	$37.20	$37.20
Purchase #5	$180.57	5.376%	$190.2774	$190.28	$190.30	$190.30
Purchase #6	$178.73	4.385%	$186.5673	$186.57	$186.55	$186.60
Purchase #7	$71.75	9.332%	$78.4457	$78.45	$78.45	$78.40
7 purchase totals =	$803.61		$848.3796	$848.38	$848.35	$848.40