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	$118.41	8.126%	$128.032	$128.03	$128.05	$128.00
Purchase #2	$56.32	5.614%	$59.4818	$59.48	$59.50	$59.50
Purchase #3	$67.94	4.868%	$71.2473	$71.25	$71.25	$71.20
Purchase #4	$8.40	3.334%	$8.6801	$8.68	$8.70	$8.70
Purchase #5	$245.94	10.166%	$270.9423	$270.94	$270.95	$270.90
Purchase #6	$137.76	13.872%	$156.8701	$156.87	$156.85	$156.90
Purchase #7	$209.65	13.640%	$238.2463	$238.25	$238.25	$238.20
7 purchase totals =	$844.42		$933.4999	$933.50	$933.55	$933.40