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	$87.72	3.745%	$91.0051	$91.01	$91.00	$91.00
Purchase #2	$160.91	11.632%	$179.6271	$179.63	$179.65	$179.60
Purchase #3	$122.89	3.298%	$126.9429	$126.94	$126.95	$126.90
Purchase #4	$36.68	10.304%	$40.4595	$40.46	$40.45	$40.50
Purchase #5	$199.79	7.662%	$215.0979	$215.10	$215.10	$215.10
Purchase #6	$112.54	9.557%	$123.2954	$123.30	$123.30	$123.30
Purchase #7	$94.44	5.298%	$99.4434	$99.44	$99.45	$99.40
7 purchase totals =	$814.97		$875.8713	$875.88	$875.90	$875.80