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	$179.43	7.320%	$192.5643	$192.56	$192.55	$192.60
Purchase #2	$122.83	11.158%	$136.5354	$136.54	$136.55	$136.50
Purchase #3	$228.76	4.121%	$238.1872	$238.19	$238.20	$238.20
Purchase #4	$93.29	10.524%	$103.1078	$103.11	$103.10	$103.10
Purchase #5	$111.74	10.822%	$123.8325	$123.83	$123.85	$123.80
Purchase #6	$101.30	9.625%	$111.0501	$111.05	$111.05	$111.10
Purchase #7	$128.92	12.289%	$144.763	$144.76	$144.75	$144.80
7 purchase totals =	$966.27		$1,050.0403	$1,050.04	$1,050.05	$1,050.10