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	$48.59	8.848%	$52.8892	$52.89	$52.90	$52.90
Purchase #2	$19.55	12.272%	$21.9492	$21.95	$21.95	$21.90
Purchase #3	$35.35	7.187%	$37.8906	$37.89	$37.90	$37.90
Purchase #4	$28.88	6.251%	$30.6853	$30.69	$30.70	$30.70
Purchase #5	$128.94	12.532%	$145.0988	$145.10	$145.10	$145.10
Purchase #6	$58.61	8.567%	$63.6311	$63.63	$63.65	$63.60
Purchase #7	$239.96	6.511%	$255.5838	$255.58	$255.60	$255.60
7 purchase totals =	$559.88		$607.7280	$607.73	$607.80	$607.70