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	$88.49	11.181%	$98.3841	$98.38	$98.40	$98.40
Purchase #2	$25.92	9.821%	$28.4656	$28.47	$28.45	$28.50
Purchase #3	$180.47	9.670%	$197.9214	$197.92	$197.90	$197.90
Purchase #4	$109.33	4.588%	$114.3461	$114.35	$114.35	$114.30
Purchase #5	$215.90	4.357%	$225.3068	$225.31	$225.30	$225.30
Purchase #6	$114.69	10.827%	$127.1075	$127.11	$127.10	$127.10
Purchase #7	$241.31	12.352%	$271.1166	$271.12	$271.10	$271.10
7 purchase totals =	$976.11		$1,062.6481	$1,062.66	$1,062.60	$1,062.60