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	$99.70	10.177%	$109.8465	$109.85	$109.85	$109.80
Purchase #2	$241.26	7.481%	$259.3087	$259.31	$259.30	$259.30
Purchase #3	$26.71	13.313%	$30.2659	$30.27	$30.25	$30.30
Purchase #4	$220.28	10.602%	$243.6341	$243.63	$243.65	$243.60
Purchase #5	$189.33	12.717%	$213.4071	$213.41	$213.40	$213.40
Purchase #6	$56.80	4.570%	$59.3958	$59.40	$59.40	$59.40
Purchase #7	$117.34	12.245%	$131.7083	$131.71	$131.70	$131.70
7 purchase totals =	$951.42		$1,047.5664	$1,047.58	$1,047.55	$1,047.50