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	$14.74	7.654%	$15.8682	$15.87	$15.85	$15.90
Purchase #2	$229.41	3.152%	$236.641	$236.64	$236.65	$236.60
Purchase #3	$242.50	8.518%	$263.1562	$263.16	$263.15	$263.20
Purchase #4	$166.54	3.251%	$171.9542	$171.95	$171.95	$172.00
Purchase #5	$54.48	9.143%	$59.4611	$59.46	$59.45	$59.50
Purchase #6	$25.94	7.745%	$27.9491	$27.95	$27.95	$27.90
Purchase #7	$215.72	7.355%	$231.5862	$231.59	$231.60	$231.60
7 purchase totals =	$949.33		$1,006.6160	$1,006.62	$1,006.60	$1,006.70