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	$59.70	8.461%	$64.7512	$64.75	$64.75	$64.80
Purchase #2	$232.86	8.107%	$251.738	$251.74	$251.75	$251.70
Purchase #3	$67.55	7.283%	$72.4697	$72.47	$72.45	$72.50
Purchase #4	$133.29	6.446%	$141.8819	$141.88	$141.90	$141.90
Purchase #5	$174.78	5.856%	$185.0151	$185.02	$185.00	$185.00
Purchase #6	$102.89	8.210%	$111.3373	$111.34	$111.35	$111.30
Purchase #7	$166.41	10.560%	$183.9829	$183.98	$184.00	$184.00
7 purchase totals =	$937.48		$1,011.1761	$1,011.18	$1,011.20	$1,011.20