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	$198.33	10.672%	$219.4958	$219.50	$219.50	$219.50
Purchase #2	$73.59	5.346%	$77.5241	$77.52	$77.50	$77.50
Purchase #3	$245.86	11.398%	$273.8831	$273.88	$273.90	$273.90
Purchase #4	$147.42	11.672%	$164.6269	$164.63	$164.65	$164.60
Purchase #5	$152.88	6.314%	$162.5328	$162.53	$162.55	$162.50
Purchase #6	$176.64	8.223%	$191.1651	$191.17	$191.15	$191.20
Purchase #7	$93.89	5.835%	$99.3685	$99.37	$99.35	$99.40
7 purchase totals =	$1,088.61		$1,188.5963	$1,188.60	$1,188.60	$1,188.60