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	$46.82	11.371%	$52.1439	$52.14	$52.15	$52.10
Purchase #2	$161.89	9.373%	$177.0639	$177.06	$177.05	$177.10
Purchase #3	$222.67	12.422%	$250.3301	$250.33	$250.35	$250.30
Purchase #4	$168.45	6.618%	$179.598	$179.60	$179.60	$179.60
Purchase #5	$79.64	13.812%	$90.6399	$90.64	$90.65	$90.60
Purchase #6	$230.71	6.269%	$245.1732	$245.17	$245.15	$245.20
Purchase #7	$95.47	3.715%	$99.0167	$99.02	$99.00	$99.00
7 purchase totals =	$1,005.65		$1,093.9657	$1,093.96	$1,093.95	$1,093.90