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	$150.43	10.634%	$166.4267	$166.43	$166.45	$166.40
Purchase #2	$48.49	13.630%	$55.0992	$55.10	$55.10	$55.10
Purchase #3	$116.45	10.642%	$128.8426	$128.84	$128.85	$128.80
Purchase #4	$186.92	7.481%	$200.9035	$200.90	$200.90	$200.90
Purchase #5	$203.56	3.544%	$210.7742	$210.77	$210.75	$210.80
Purchase #6	$206.92	11.843%	$231.4255	$231.43	$231.45	$231.40
Purchase #7	$180.40	4.415%	$188.3647	$188.36	$188.35	$188.40
7 purchase totals =	$1,093.17		$1,181.8364	$1,181.83	$1,181.85	$1,181.80