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	$36.45	12.820%	$41.1229	$41.12	$41.10	$41.10
Purchase #2	$143.45	6.569%	$152.8732	$152.87	$152.85	$152.90
Purchase #3	$247.96	10.471%	$273.9239	$273.92	$273.90	$273.90
Purchase #4	$212.60	13.542%	$241.3903	$241.39	$241.40	$241.40
Purchase #5	$225.78	12.331%	$253.6209	$253.62	$253.60	$253.60
Purchase #6	$248.57	3.450%	$257.1457	$257.15	$257.15	$257.10
Purchase #7	$27.41	3.779%	$28.4458	$28.45	$28.45	$28.40
7 purchase totals =	$1,142.22		$1,248.5227	$1,248.52	$1,248.45	$1,248.40