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	$212.34	3.238%	$219.2156	$219.22	$219.20	$219.20
Purchase #2	$7.71	12.216%	$8.6519	$8.65	$8.65	$8.70
Purchase #3	$28.30	3.447%	$29.2755	$29.28	$29.30	$29.30
Purchase #4	$86.46	4.484%	$90.3369	$90.34	$90.35	$90.30
Purchase #5	$136.96	8.682%	$148.8509	$148.85	$148.85	$148.90
Purchase #6	$133.69	6.236%	$142.0269	$142.03	$142.05	$142.00
Purchase #7	$204.82	8.135%	$221.4821	$221.48	$221.50	$221.50
7 purchase totals =	$810.28		$859.8398	$859.85	$859.90	$859.90