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	$181.33	7.330%	$194.6215	$194.62	$194.60	$194.60
Purchase #2	$52.83	12.701%	$59.5399	$59.54	$59.55	$59.50
Purchase #3	$245.82	6.501%	$261.8008	$261.80	$261.80	$261.80
Purchase #4	$148.93	9.285%	$162.7582	$162.76	$162.75	$162.80
Purchase #5	$52.87	4.241%	$55.1122	$55.11	$55.10	$55.10
Purchase #6	$244.98	10.507%	$270.72	$270.72	$270.70	$270.70
Purchase #7	$138.98	3.467%	$143.7984	$143.80	$143.80	$143.80
7 purchase totals =	$1,065.74		$1,148.3510	$1,148.35	$1,148.30	$1,148.30