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	$106.32	7.442%	$114.2323	$114.23	$114.25	$114.20
Purchase #2	$146.63	4.685%	$153.4996	$153.50	$153.50	$153.50
Purchase #3	$171.26	11.754%	$191.3899	$191.39	$191.40	$191.40
Purchase #4	$105.35	9.603%	$115.4668	$115.47	$115.45	$115.50
Purchase #5	$167.71	10.812%	$185.8428	$185.84	$185.85	$185.80
Purchase #6	$145.46	3.291%	$150.2471	$150.25	$150.25	$150.20
Purchase #7	$96.75	8.338%	$104.817	$104.82	$104.80	$104.80
7 purchase totals =	$939.48		$1,015.4955	$1,015.50	$1,015.50	$1,015.40