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	$97.98	13.560%	$111.2661	$111.27	$111.25	$111.30
Purchase #2	$244.92	9.866%	$269.0838	$269.08	$269.10	$269.10
Purchase #3	$116.49	4.156%	$121.3313	$121.33	$121.35	$121.30
Purchase #4	$199.98	9.129%	$218.2362	$218.24	$218.25	$218.20
Purchase #5	$145.31	3.637%	$150.5949	$150.59	$150.60	$150.60
Purchase #6	$35.82	3.505%	$37.0755	$37.08	$37.10	$37.10
Purchase #7	$175.88	6.166%	$186.7248	$186.72	$186.70	$186.70
7 purchase totals =	$1,016.38		$1,094.3126	$1,094.31	$1,094.35	$1,094.30