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	$247.88	8.219%	$268.2533	$268.25	$268.25	$268.30
Purchase #2	$78.33	3.837%	$81.3355	$81.34	$81.35	$81.30
Purchase #3	$48.85	6.166%	$51.8621	$51.86	$51.85	$51.90
Purchase #4	$185.57	6.155%	$196.9918	$196.99	$197.00	$197.00
Purchase #5	$33.33	13.387%	$37.7919	$37.79	$37.80	$37.80
Purchase #6	$52.46	13.745%	$59.6706	$59.67	$59.65	$59.70
Purchase #7	$188.37	13.462%	$213.7284	$213.73	$213.75	$213.70
7 purchase totals =	$834.79		$909.6336	$909.63	$909.65	$909.70