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	$125.65	11.298%	$139.8459	$139.85	$139.85	$139.80
Purchase #2	$51.54	11.401%	$57.4161	$57.42	$57.40	$57.40
Purchase #3	$91.33	9.428%	$99.9406	$99.94	$99.95	$99.90
Purchase #4	$171.32	9.412%	$187.4446	$187.44	$187.45	$187.40
Purchase #5	$171.42	11.728%	$191.5241	$191.52	$191.50	$191.50
Purchase #6	$141.30	8.784%	$153.7118	$153.71	$153.70	$153.70
Purchase #7	$187.25	10.348%	$206.6266	$206.63	$206.65	$206.60
7 purchase totals =	$939.81		$1,036.5097	$1,036.51	$1,036.50	$1,036.30