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	$55.81	6.333%	$59.3444	$59.34	$59.35	$59.30
Purchase #2	$69.41	5.292%	$73.0832	$73.08	$73.10	$73.10
Purchase #3	$50.63	13.227%	$57.3268	$57.33	$57.35	$57.30
Purchase #4	$96.66	3.737%	$100.2722	$100.27	$100.25	$100.30
Purchase #5	$64.27	5.236%	$67.6352	$67.64	$67.65	$67.60
Purchase #6	$29.72	4.110%	$30.9415	$30.94	$30.95	$30.90
Purchase #7	$90.33	11.255%	$100.4966	$100.50	$100.50	$100.50
7 purchase totals =	$456.83		$489.0999	$489.10	$489.15	$489.00