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	$103.96	6.867%	$111.0989	$111.10	$111.10	$111.10
Purchase #2	$108.27	4.807%	$113.4745	$113.47	$113.45	$113.50
Purchase #3	$120.28	9.122%	$131.2519	$131.25	$131.25	$131.30
Purchase #4	$151.35	7.213%	$162.2669	$162.27	$162.25	$162.30
Purchase #5	$147.51	12.647%	$166.1656	$166.17	$166.15	$166.20
Purchase #6	$223.85	5.174%	$235.432	$235.43	$235.45	$235.40
Purchase #7	$240.43	3.380%	$248.5565	$248.56	$248.55	$248.60
7 purchase totals =	$1,095.65		$1,168.2463	$1,168.25	$1,168.20	$1,168.40