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	$46.69	7.527%	$50.2044	$50.20	$50.20	$50.20
Purchase #2	$61.66	5.839%	$65.2603	$65.26	$65.25	$65.30
Purchase #3	$227.53	6.778%	$242.952	$242.95	$242.95	$243.00
Purchase #4	$176.68	8.421%	$191.5582	$191.56	$191.55	$191.60
Purchase #5	$136.64	3.457%	$141.3636	$141.36	$141.35	$141.40
Purchase #6	$131.62	10.807%	$145.8442	$145.84	$145.85	$145.80
Purchase #7	$190.49	3.275%	$196.7285	$196.73	$196.75	$196.70
7 purchase totals =	$971.31		$1,033.9112	$1,033.90	$1,033.90	$1,034.00