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	$13.43	6.280%	$14.2734	$14.27	$14.25	$14.30
Purchase #2	$173.25	3.867%	$179.9496	$179.95	$179.95	$179.90
Purchase #3	$141.75	4.802%	$148.5568	$148.56	$148.55	$148.60
Purchase #4	$98.46	6.865%	$105.2193	$105.22	$105.20	$105.20
Purchase #5	$154.59	9.333%	$169.0179	$169.02	$169.00	$169.00
Purchase #6	$45.56	5.236%	$47.9455	$47.95	$47.95	$47.90
Purchase #7	$120.66	5.751%	$127.5992	$127.60	$127.60	$127.60
7 purchase totals =	$747.70		$792.5617	$792.57	$792.50	$792.50