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	$187.57	13.275%	$212.4699	$212.47	$212.45	$212.50
Purchase #2	$51.52	5.395%	$54.2995	$54.30	$54.30	$54.30
Purchase #3	$229.54	4.619%	$240.1425	$240.14	$240.15	$240.10
Purchase #4	$240.66	12.250%	$270.1409	$270.14	$270.15	$270.10
Purchase #5	$157.31	4.591%	$164.5321	$164.53	$164.55	$164.50
Purchase #6	$177.75	6.568%	$189.4246	$189.42	$189.40	$189.40
Purchase #7	$45.95	6.407%	$48.894	$48.89	$48.90	$48.90
7 purchase totals =	$1,090.30		$1,179.9035	$1,179.89	$1,179.90	$1,179.80