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	$241.87	3.467%	$250.2556	$250.26	$250.25	$250.30
Purchase #2	$162.90	4.311%	$169.9226	$169.92	$169.90	$169.90
Purchase #3	$117.44	8.421%	$127.3296	$127.33	$127.35	$127.30
Purchase #4	$91.84	5.208%	$96.623	$96.62	$96.60	$96.60
Purchase #5	$122.58	9.503%	$134.2288	$134.23	$134.25	$134.20
Purchase #6	$113.56	3.300%	$117.3075	$117.31	$117.30	$117.30
Purchase #7	$106.99	12.757%	$120.6387	$120.64	$120.65	$120.60
7 purchase totals =	$957.18		$1,016.3058	$1,016.31	$1,016.30	$1,016.20