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	$221.51	3.357%	$228.9461	$228.95	$228.95	$228.90
Purchase #2	$162.30	3.683%	$168.2775	$168.28	$168.30	$168.30
Purchase #3	$134.80	11.350%	$150.0998	$150.10	$150.10	$150.10
Purchase #4	$174.86	5.250%	$184.0402	$184.04	$184.05	$184.00
Purchase #5	$175.89	5.451%	$185.4778	$185.48	$185.50	$185.50
Purchase #6	$64.37	13.263%	$72.9074	$72.91	$72.90	$72.90
Purchase #7	$26.64	3.725%	$27.6323	$27.63	$27.65	$27.60
7 purchase totals =	$960.37		$1,017.3811	$1,017.39	$1,017.45	$1,017.30