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	$87.92	11.115%	$97.6923	$97.69	$97.70	$97.70
Purchase #2	$34.31	3.582%	$35.539	$35.54	$35.55	$35.50
Purchase #3	$114.98	7.400%	$123.4885	$123.49	$123.50	$123.50
Purchase #4	$165.98	9.184%	$181.2236	$181.22	$181.20	$181.20
Purchase #5	$225.60	7.815%	$243.2306	$243.23	$243.25	$243.20
Purchase #6	$133.52	9.587%	$146.3206	$146.32	$146.30	$146.30
Purchase #7	$185.73	5.575%	$196.0844	$196.08	$196.10	$196.10
7 purchase totals =	$948.04		$1,023.5790	$1,023.57	$1,023.60	$1,023.50