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	$145.31	13.844%	$165.4267	$165.43	$165.45	$165.40
Purchase #2	$115.90	10.686%	$128.2851	$128.29	$128.30	$128.30
Purchase #3	$100.32	3.844%	$104.1763	$104.18	$104.20	$104.20
Purchase #4	$194.35	9.672%	$213.1475	$213.15	$213.15	$213.10
Purchase #5	$172.96	9.464%	$189.3289	$189.33	$189.35	$189.30
Purchase #6	$116.89	3.789%	$121.319	$121.32	$121.30	$121.30
Purchase #7	$212.66	4.687%	$222.6274	$222.63	$222.65	$222.60
7 purchase totals =	$1,058.39		$1,144.3109	$1,144.33	$1,144.40	$1,144.20