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	$111.59	5.450%	$117.6717	$117.67	$117.65	$117.70
Purchase #2	$54.53	9.567%	$59.7469	$59.75	$59.75	$59.70
Purchase #3	$117.99	4.332%	$123.1013	$123.10	$123.10	$123.10
Purchase #4	$126.53	12.259%	$142.0413	$142.04	$142.05	$142.00
Purchase #5	$28.27	12.121%	$31.6966	$31.70	$31.70	$31.70
Purchase #6	$47.74	5.787%	$50.5027	$50.50	$50.50	$50.50
Purchase #7	$208.76	7.137%	$223.6592	$223.66	$223.65	$223.70
7 purchase totals =	$695.41		$748.4197	$748.42	$748.40	$748.40