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	$205.26	11.437%	$228.7356	$228.74	$228.75	$228.70
Purchase #2	$71.50	11.551%	$79.759	$79.76	$79.75	$79.80
Purchase #3	$248.72	12.769%	$280.4791	$280.48	$280.50	$280.50
Purchase #4	$42.82	10.127%	$47.1564	$47.16	$47.15	$47.20
Purchase #5	$68.38	13.698%	$77.7467	$77.75	$77.75	$77.70
Purchase #6	$165.31	8.347%	$179.1084	$179.11	$179.10	$179.10
Purchase #7	$115.77	6.410%	$123.1909	$123.19	$123.20	$123.20
7 purchase totals =	$917.76		$1,016.1761	$1,016.19	$1,016.20	$1,016.20