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	$209.49	9.185%	$228.7317	$228.73	$228.75	$228.70
Purchase #2	$178.35	3.595%	$184.7617	$184.76	$184.75	$184.80
Purchase #3	$225.77	5.642%	$238.5079	$238.51	$238.50	$238.50
Purchase #4	$62.73	4.259%	$65.4017	$65.40	$65.40	$65.40
Purchase #5	$72.54	11.199%	$80.6638	$80.66	$80.65	$80.70
Purchase #6	$222.63	4.872%	$233.4765	$233.48	$233.50	$233.50
Purchase #7	$72.57	7.524%	$78.0302	$78.03	$78.05	$78.00
7 purchase totals =	$1,044.08		$1,109.5735	$1,109.57	$1,109.60	$1,109.60