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	$67.43	7.508%	$72.4926	$72.49	$72.50	$72.50
Purchase #2	$113.59	11.857%	$127.0584	$127.06	$127.05	$127.10
Purchase #3	$86.41	11.640%	$96.4681	$96.47	$96.45	$96.50
Purchase #4	$193.59	11.813%	$216.4588	$216.46	$216.45	$216.50
Purchase #5	$139.80	3.318%	$144.4386	$144.44	$144.45	$144.40
Purchase #6	$152.85	3.665%	$158.452	$158.45	$158.45	$158.50
Purchase #7	$69.68	13.544%	$79.1175	$79.12	$79.10	$79.10
7 purchase totals =	$823.35		$894.4860	$894.49	$894.45	$894.60