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	$141.59	9.767%	$155.4191	$155.42	$155.40	$155.40
Purchase #2	$236.32	3.390%	$244.3312	$244.33	$244.35	$244.30
Purchase #3	$31.48	9.732%	$34.5436	$34.54	$34.55	$34.50
Purchase #4	$167.83	10.410%	$185.3011	$185.30	$185.30	$185.30
Purchase #5	$106.97	6.712%	$114.1498	$114.15	$114.15	$114.10
Purchase #6	$38.40	9.754%	$42.1455	$42.15	$42.15	$42.10
Purchase #7	$244.39	10.419%	$269.853	$269.85	$269.85	$269.90
7 purchase totals =	$966.98		$1,045.7433	$1,045.74	$1,045.75	$1,045.60