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	$225.99	10.685%	$250.137	$250.14	$250.15	$250.10
Purchase #2	$176.26	3.743%	$182.8574	$182.86	$182.85	$182.90
Purchase #3	$82.38	8.753%	$89.5907	$89.59	$89.60	$89.60
Purchase #4	$99.40	13.118%	$112.4393	$112.44	$112.45	$112.40
Purchase #5	$227.29	9.286%	$248.3961	$248.40	$248.40	$248.40
Purchase #6	$241.77	3.180%	$249.4583	$249.46	$249.45	$249.50
Purchase #7	$214.29	5.192%	$225.4159	$225.42	$225.40	$225.40
7 purchase totals =	$1,267.38		$1,358.2947	$1,358.31	$1,358.30	$1,358.30