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	$73.42	7.107%	$78.638	$78.64	$78.65	$78.60
Purchase #2	$136.52	4.225%	$142.288	$142.29	$142.30	$142.30
Purchase #3	$108.56	4.617%	$113.5722	$113.57	$113.55	$113.60
Purchase #4	$245.83	5.586%	$259.5621	$259.56	$259.55	$259.60
Purchase #5	$114.88	12.348%	$129.0654	$129.07	$129.05	$129.10
Purchase #6	$173.38	8.393%	$187.9318	$187.93	$187.95	$187.90
Purchase #7	$159.49	7.134%	$170.868	$170.87	$170.85	$170.90
7 purchase totals =	$1,012.08		$1,081.9255	$1,081.93	$1,081.90	$1,082.00