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	$106.52	5.586%	$112.4702	$112.47	$112.45	$112.50
Purchase #2	$78.27	5.472%	$82.5529	$82.55	$82.55	$82.60
Purchase #3	$177.75	10.604%	$196.5986	$196.60	$196.60	$196.60
Purchase #4	$83.44	13.595%	$94.7837	$94.78	$94.80	$94.80
Purchase #5	$187.83	9.609%	$205.8786	$205.88	$205.90	$205.90
Purchase #6	$53.69	11.378%	$59.7988	$59.80	$59.80	$59.80
Purchase #7	$28.67	6.289%	$30.4731	$30.47	$30.45	$30.50
7 purchase totals =	$716.17		$782.5559	$782.55	$782.55	$782.70