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	$226.35	12.708%	$255.1146	$255.11	$255.10	$255.10
Purchase #2	$249.94	12.136%	$280.2727	$280.27	$280.25	$280.30
Purchase #3	$99.68	5.623%	$105.285	$105.29	$105.30	$105.30
Purchase #4	$55.52	11.269%	$61.7765	$61.78	$61.80	$61.80
Purchase #5	$53.77	8.166%	$58.1609	$58.16	$58.15	$58.20
Purchase #6	$64.67	7.403%	$69.4575	$69.46	$69.45	$69.50
Purchase #7	$168.31	9.493%	$184.2877	$184.29	$184.30	$184.30
7 purchase totals =	$918.24		$1,014.3549	$1,014.36	$1,014.35	$1,014.50