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	$81.74	8.578%	$88.7517	$88.75	$88.75	$88.80
Purchase #2	$65.85	5.654%	$69.5732	$69.57	$69.55	$69.60
Purchase #3	$165.26	8.200%	$178.8113	$178.81	$178.80	$178.80
Purchase #4	$211.67	5.161%	$222.5943	$222.59	$222.60	$222.60
Purchase #5	$51.33	4.391%	$53.5839	$53.58	$53.60	$53.60
Purchase #6	$242.56	5.170%	$255.1004	$255.10	$255.10	$255.10
Purchase #7	$186.46	5.157%	$196.0757	$196.08	$196.10	$196.10
7 purchase totals =	$1,004.87		$1,064.4905	$1,064.48	$1,064.50	$1,064.60