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	$60.37	3.473%	$62.4667	$62.47	$62.45	$62.50
Purchase #2	$130.80	11.817%	$146.2566	$146.26	$146.25	$146.30
Purchase #3	$226.57	12.764%	$255.4894	$255.49	$255.50	$255.50
Purchase #4	$91.85	6.824%	$98.1178	$98.12	$98.10	$98.10
Purchase #5	$179.39	10.421%	$198.0842	$198.08	$198.10	$198.10
Purchase #6	$243.46	12.365%	$273.5638	$273.56	$273.55	$273.60
Purchase #7	$211.87	8.517%	$229.915	$229.92	$229.90	$229.90
7 purchase totals =	$1,144.31		$1,263.8935	$1,263.90	$1,263.85	$1,264.00