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	$186.82	6.765%	$199.4584	$199.46	$199.45	$199.50
Purchase #2	$228.29	12.653%	$257.1755	$257.18	$257.20	$257.20
Purchase #3	$63.67	12.461%	$71.6039	$71.60	$71.60	$71.60
Purchase #4	$160.41	6.663%	$171.0981	$171.10	$171.10	$171.10
Purchase #5	$110.73	6.131%	$117.5189	$117.52	$117.50	$117.50
Purchase #6	$64.89	13.357%	$73.5574	$73.56	$73.55	$73.60
Purchase #7	$174.87	7.770%	$188.4574	$188.46	$188.45	$188.50
7 purchase totals =	$989.68		$1,078.8696	$1,078.88	$1,078.85	$1,079.00