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	$96.94	9.203%	$105.8614	$105.86	$105.85	$105.90
Purchase #2	$93.30	10.461%	$103.0601	$103.06	$103.05	$103.10
Purchase #3	$33.35	11.436%	$37.1639	$37.16	$37.15	$37.20
Purchase #4	$201.48	12.785%	$227.2392	$227.24	$227.25	$227.20
Purchase #5	$135.64	5.302%	$142.8316	$142.83	$142.85	$142.80
Purchase #6	$185.88	12.735%	$209.5518	$209.55	$209.55	$209.60
Purchase #7	$225.89	9.171%	$246.6064	$246.61	$246.60	$246.60
7 purchase totals =	$972.48		$1,072.3144	$1,072.31	$1,072.30	$1,072.40