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	$67.78	6.197%	$71.9803	$71.98	$72.00	$72.00
Purchase #2	$158.71	6.152%	$168.4738	$168.47	$168.45	$168.50
Purchase #3	$250.93	12.334%	$281.8797	$281.88	$281.90	$281.90
Purchase #4	$106.71	8.680%	$115.9724	$115.97	$115.95	$116.00
Purchase #5	$106.46	3.755%	$110.4576	$110.46	$110.45	$110.50
Purchase #6	$125.50	4.756%	$131.4688	$131.47	$131.45	$131.50
Purchase #7	$172.89	4.351%	$180.4124	$180.41	$180.40	$180.40
7 purchase totals =	$988.98		$1,060.6450	$1,060.64	$1,060.60	$1,060.80