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	$170.43	11.258%	$189.617	$189.62	$189.60	$189.60
Purchase #2	$122.69	12.581%	$138.1256	$138.13	$138.15	$138.10
Purchase #3	$208.76	3.116%	$215.265	$215.27	$215.25	$215.30
Purchase #4	$116.44	8.264%	$126.0626	$126.06	$126.05	$126.10
Purchase #5	$179.49	13.601%	$203.9024	$203.90	$203.90	$203.90
Purchase #6	$106.74	4.436%	$111.475	$111.48	$111.50	$111.50
Purchase #7	$101.39	4.144%	$105.5916	$105.59	$105.60	$105.60
7 purchase totals =	$1,005.94		$1,090.0392	$1,090.05	$1,090.05	$1,090.10