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	$215.36	10.587%	$238.1602	$238.16	$238.15	$238.20
Purchase #2	$36.75	5.140%	$38.639	$38.64	$38.65	$38.60
Purchase #3	$80.43	5.492%	$84.8472	$84.85	$84.85	$84.80
Purchase #4	$142.88	6.510%	$152.1815	$152.18	$152.20	$152.20
Purchase #5	$168.63	12.174%	$189.159	$189.16	$189.15	$189.20
Purchase #6	$230.36	12.634%	$259.4637	$259.46	$259.45	$259.50
Purchase #7	$158.40	13.281%	$179.4371	$179.44	$179.45	$179.40
7 purchase totals =	$1,032.81		$1,141.8877	$1,141.89	$1,141.90	$1,141.90