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	$72.98	12.371%	$82.0084	$82.01	$82.00	$82.00
Purchase #2	$67.82	6.249%	$72.0581	$72.06	$72.05	$72.10
Purchase #3	$178.76	4.215%	$186.2947	$186.29	$186.30	$186.30
Purchase #4	$131.31	12.431%	$147.6331	$147.63	$147.65	$147.60
Purchase #5	$189.32	4.808%	$198.4225	$198.42	$198.40	$198.40
Purchase #6	$211.86	11.611%	$236.4591	$236.46	$236.45	$236.50
Purchase #7	$171.67	3.775%	$178.1505	$178.15	$178.15	$178.20
7 purchase totals =	$1,023.72		$1,101.0264	$1,101.02	$1,101.00	$1,101.10