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	$156.41	9.693%	$171.5708	$171.57	$171.55	$171.60
Purchase #2	$65.27	5.485%	$68.8501	$68.85	$68.85	$68.90
Purchase #3	$89.52	12.258%	$100.4934	$100.49	$100.50	$100.50
Purchase #4	$102.36	10.141%	$112.7403	$112.74	$112.75	$112.70
Purchase #5	$210.51	6.745%	$224.7089	$224.71	$224.70	$224.70
Purchase #6	$77.66	11.349%	$86.4736	$86.47	$86.45	$86.50
Purchase #7	$69.51	3.198%	$71.7329	$71.73	$71.75	$71.70
7 purchase totals =	$771.24		$836.5700	$836.56	$836.55	$836.60