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	$157.41	8.712%	$171.1236	$171.12	$171.10	$171.10
Purchase #2	$12.57	6.811%	$13.4261	$13.43	$13.45	$13.40
Purchase #3	$47.74	13.656%	$54.2594	$54.26	$54.25	$54.30
Purchase #4	$132.76	11.824%	$148.4575	$148.46	$148.45	$148.50
Purchase #5	$5.74	12.280%	$6.4449	$6.44	$6.45	$6.40
Purchase #6	$196.33	10.846%	$217.624	$217.62	$217.60	$217.60
Purchase #7	$94.57	9.477%	$103.5324	$103.53	$103.55	$103.50
7 purchase totals =	$647.12		$714.8679	$714.86	$714.85	$714.80