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	$239.60	10.280%	$264.2309	$264.23	$264.25	$264.20
Purchase #2	$61.49	7.505%	$66.1048	$66.10	$66.10	$66.10
Purchase #3	$245.50	6.602%	$261.7079	$261.71	$261.70	$261.70
Purchase #4	$77.25	6.820%	$82.5185	$82.52	$82.50	$82.50
Purchase #5	$101.63	7.720%	$109.4758	$109.48	$109.50	$109.50
Purchase #6	$237.72	10.467%	$262.6022	$262.60	$262.60	$262.60
Purchase #7	$49.57	12.515%	$55.7737	$55.77	$55.75	$55.80
7 purchase totals =	$1,012.76		$1,102.4138	$1,102.41	$1,102.40	$1,102.40