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	$40.46	11.444%	$45.0902	$45.09	$45.10	$45.10
Purchase #2	$68.52	11.763%	$76.58	$76.58	$76.60	$76.60
Purchase #3	$176.68	4.298%	$184.2737	$184.27	$184.25	$184.30
Purchase #4	$202.33	12.849%	$228.3274	$228.33	$228.35	$228.30
Purchase #5	$211.52	10.422%	$233.5646	$233.56	$233.55	$233.60
Purchase #6	$162.49	7.632%	$174.8912	$174.89	$174.90	$174.90
Purchase #7	$191.33	3.817%	$198.6331	$198.63	$198.65	$198.60
7 purchase totals =	$1,053.33		$1,141.3602	$1,141.35	$1,141.40	$1,141.40