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	$47.38	11.480%	$52.8192	$52.82	$52.80	$52.80
Purchase #2	$232.34	9.813%	$255.1395	$255.14	$255.15	$255.10
Purchase #3	$130.39	7.371%	$140.001	$140.00	$140.00	$140.00
Purchase #4	$178.73	9.706%	$196.0775	$196.08	$196.10	$196.10
Purchase #5	$98.46	5.696%	$104.0683	$104.07	$104.05	$104.10
Purchase #6	$91.36	13.818%	$103.9841	$103.98	$104.00	$104.00
Purchase #7	$188.91	3.556%	$195.6276	$195.63	$195.65	$195.60
7 purchase totals =	$967.57		$1,047.7172	$1,047.72	$1,047.75	$1,047.70