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	$63.39	13.159%	$71.7315	$71.73	$71.75	$71.70
Purchase #2	$139.72	10.194%	$153.9631	$153.96	$153.95	$154.00
Purchase #3	$184.66	11.384%	$205.6817	$205.68	$205.70	$205.70
Purchase #4	$215.64	11.420%	$240.2661	$240.27	$240.25	$240.30
Purchase #5	$96.33	8.637%	$104.65	$104.65	$104.65	$104.70
Purchase #6	$191.88	4.407%	$200.3362	$200.34	$200.35	$200.30
Purchase #7	$116.59	12.580%	$131.257	$131.26	$131.25	$131.30
7 purchase totals =	$1,008.21		$1,107.8856	$1,107.89	$1,107.90	$1,108.00