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	$70.88	11.401%	$78.961	$78.96	$78.95	$79.00
Purchase #2	$53.46	10.517%	$59.0824	$59.08	$59.10	$59.10
Purchase #3	$36.32	5.614%	$38.359	$38.36	$38.35	$38.40
Purchase #4	$8.71	5.799%	$9.2151	$9.22	$9.20	$9.20
Purchase #5	$192.60	12.138%	$215.9778	$215.98	$216.00	$216.00
Purchase #6	$66.85	6.376%	$71.1124	$71.11	$71.10	$71.10
Purchase #7	$98.98	12.813%	$111.6623	$111.66	$111.65	$111.70
7 purchase totals =	$527.80		$584.3700	$584.37	$584.35	$584.50