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	$95.70	8.527%	$103.8603	$103.86	$103.85	$103.90
Purchase #2	$245.65	6.304%	$261.1358	$261.14	$261.15	$261.10
Purchase #3	$91.55	10.135%	$100.8286	$100.83	$100.85	$100.80
Purchase #4	$143.55	12.685%	$161.7593	$161.76	$161.75	$161.80
Purchase #5	$203.71	8.512%	$221.0498	$221.05	$221.05	$221.00
Purchase #6	$89.83	10.209%	$99.0007	$99.00	$99.00	$99.00
Purchase #7	$147.82	11.210%	$164.3906	$164.39	$164.40	$164.40
7 purchase totals =	$1,017.81		$1,112.0251	$1,112.03	$1,112.05	$1,112.00