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	$247.88	5.649%	$261.8827	$261.88	$261.90	$261.90
Purchase #2	$16.33	7.540%	$17.5613	$17.56	$17.55	$17.60
Purchase #3	$37.55	4.178%	$39.1188	$39.12	$39.10	$39.10
Purchase #4	$163.98	9.209%	$179.0809	$179.08	$179.10	$179.10
Purchase #5	$209.27	3.510%	$216.6154	$216.62	$216.60	$216.60
Purchase #6	$203.93	7.525%	$219.2757	$219.28	$219.30	$219.30
Purchase #7	$123.52	3.818%	$128.236	$128.24	$128.25	$128.20
7 purchase totals =	$1,002.46		$1,061.7708	$1,061.78	$1,061.80	$1,061.80