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	$81.71	4.714%	$85.5618	$85.56	$85.55	$85.60
Purchase #2	$119.67	8.209%	$129.4937	$129.49	$129.50	$129.50
Purchase #3	$243.80	11.397%	$271.5859	$271.59	$271.60	$271.60
Purchase #4	$198.68	8.374%	$215.3175	$215.32	$215.30	$215.30
Purchase #5	$236.45	3.184%	$243.9786	$243.98	$244.00	$244.00
Purchase #6	$152.80	10.848%	$169.3757	$169.38	$169.40	$169.40
Purchase #7	$43.27	8.108%	$46.7783	$46.78	$46.80	$46.80
7 purchase totals =	$1,076.38		$1,162.0915	$1,162.10	$1,162.15	$1,162.20