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	$196.84	9.590%	$215.717	$215.72	$215.70	$215.70
Purchase #2	$127.70	6.792%	$136.3734	$136.37	$136.35	$136.40
Purchase #3	$203.47	8.670%	$221.1108	$221.11	$221.10	$221.10
Purchase #4	$183.52	7.276%	$196.8729	$196.87	$196.85	$196.90
Purchase #5	$195.70	9.730%	$214.7416	$214.74	$214.75	$214.70
Purchase #6	$31.99	9.649%	$35.0767	$35.08	$35.10	$35.10
Purchase #7	$71.32	12.850%	$80.4846	$80.48	$80.50	$80.50
7 purchase totals =	$1,010.54		$1,100.3770	$1,100.37	$1,100.35	$1,100.40