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	$164.32	11.288%	$182.8684	$182.87	$182.85	$182.90
Purchase #2	$50.28	12.417%	$56.5233	$56.52	$56.50	$56.50
Purchase #3	$219.36	11.424%	$244.4197	$244.42	$244.40	$244.40
Purchase #4	$167.83	7.170%	$179.8634	$179.86	$179.85	$179.90
Purchase #5	$51.65	4.534%	$53.9918	$53.99	$54.00	$54.00
Purchase #6	$96.27	13.633%	$109.3945	$109.39	$109.40	$109.40
Purchase #7	$44.92	8.635%	$48.7988	$48.80	$48.80	$48.80
7 purchase totals =	$794.63		$875.8599	$875.85	$875.80	$875.90