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	$193.95	13.193%	$219.5378	$219.54	$219.55	$219.50
Purchase #2	$79.29	12.764%	$89.4106	$89.41	$89.40	$89.40
Purchase #3	$218.38	11.564%	$243.6335	$243.63	$243.65	$243.60
Purchase #4	$237.55	8.632%	$258.0553	$258.06	$258.05	$258.10
Purchase #5	$45.43	13.211%	$51.4318	$51.43	$51.45	$51.40
Purchase #6	$64.26	11.817%	$71.8536	$71.85	$71.85	$71.90
Purchase #7	$137.51	6.833%	$146.9061	$146.91	$146.90	$146.90
7 purchase totals =	$976.37		$1,080.8287	$1,080.83	$1,080.85	$1,080.80