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	$203.56	6.827%	$217.457	$217.46	$217.45	$217.50
Purchase #2	$48.87	11.421%	$54.4514	$54.45	$54.45	$54.50
Purchase #3	$110.95	8.499%	$120.3796	$120.38	$120.40	$120.40
Purchase #4	$194.45	9.683%	$213.2786	$213.28	$213.30	$213.30
Purchase #5	$247.96	4.119%	$258.1735	$258.17	$258.15	$258.20
Purchase #6	$58.83	11.152%	$65.3907	$65.39	$65.40	$65.40
Purchase #7	$64.57	10.633%	$71.4357	$71.44	$71.45	$71.40
7 purchase totals =	$929.19		$1,000.5665	$1,000.57	$1,000.60	$1,000.70