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	$10.65	10.498%	$11.768	$11.77	$11.75	$11.80
Purchase #2	$28.99	11.701%	$32.3821	$32.38	$32.40	$32.40
Purchase #3	$86.89	3.704%	$90.1084	$90.11	$90.10	$90.10
Purchase #4	$85.79	10.623%	$94.9035	$94.90	$94.90	$94.90
Purchase #5	$236.52	8.134%	$255.7585	$255.76	$255.75	$255.80
Purchase #6	$99.36	8.381%	$107.6874	$107.69	$107.70	$107.70
Purchase #7	$246.39	3.443%	$254.8732	$254.87	$254.85	$254.90
7 purchase totals =	$794.59		$847.4811	$847.48	$847.45	$847.60