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	$220.74	4.813%	$231.3642	$231.36	$231.35	$231.40
Purchase #2	$82.82	3.297%	$85.5506	$85.55	$85.55	$85.60
Purchase #3	$104.42	10.212%	$115.0834	$115.08	$115.10	$115.10
Purchase #4	$198.68	10.241%	$219.0268	$219.03	$219.05	$219.00
Purchase #5	$155.88	6.196%	$165.5383	$165.54	$165.55	$165.50
Purchase #6	$150.85	6.837%	$161.1636	$161.16	$161.15	$161.20
Purchase #7	$135.69	10.639%	$150.1261	$150.13	$150.15	$150.10
7 purchase totals =	$1,049.08		$1,127.8530	$1,127.85	$1,127.90	$1,127.90