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	$66.36	7.112%	$71.0795	$71.08	$71.10	$71.10
Purchase #2	$239.99	6.163%	$254.7806	$254.78	$254.80	$254.80
Purchase #3	$88.95	4.108%	$92.6041	$92.60	$92.60	$92.60
Purchase #4	$95.88	4.868%	$100.5474	$100.55	$100.55	$100.50
Purchase #5	$13.88	13.828%	$15.7993	$15.80	$15.80	$15.80
Purchase #6	$113.35	3.729%	$117.5768	$117.58	$117.60	$117.60
Purchase #7	$199.57	11.399%	$222.319	$222.32	$222.30	$222.30
7 purchase totals =	$817.98		$874.7067	$874.71	$874.75	$874.70