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	$225.36	7.835%	$243.017	$243.02	$243.00	$243.00
Purchase #2	$193.91	3.240%	$200.1927	$200.19	$200.20	$200.20
Purchase #3	$59.58	13.221%	$67.4571	$67.46	$67.45	$67.50
Purchase #4	$114.44	11.318%	$127.3923	$127.39	$127.40	$127.40
Purchase #5	$56.71	13.238%	$64.2173	$64.22	$64.20	$64.20
Purchase #6	$162.44	12.238%	$182.3194	$182.32	$182.30	$182.30
Purchase #7	$242.57	13.799%	$276.0422	$276.04	$276.05	$276.00
7 purchase totals =	$1,055.01		$1,160.6380	$1,160.64	$1,160.60	$1,160.60