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	$250.54	11.303%	$278.8585	$278.86	$278.85	$278.90
Purchase #2	$30.75	3.652%	$31.873	$31.87	$31.85	$31.90
Purchase #3	$215.82	4.266%	$225.0269	$225.03	$225.05	$225.00
Purchase #4	$109.42	7.254%	$117.3573	$117.36	$117.35	$117.40
Purchase #5	$235.69	5.759%	$249.2634	$249.26	$249.25	$249.30
Purchase #6	$174.68	4.480%	$182.5057	$182.51	$182.50	$182.50
Purchase #7	$85.69	4.814%	$89.8151	$89.82	$89.80	$89.80
7 purchase totals =	$1,102.59		$1,174.6999	$1,174.71	$1,174.65	$1,174.80