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	$88.96	8.739%	$96.7342	$96.73	$96.75	$96.70
Purchase #2	$70.61	3.227%	$72.8886	$72.89	$72.90	$72.90
Purchase #3	$225.51	7.788%	$243.0727	$243.07	$243.05	$243.10
Purchase #4	$73.60	6.291%	$78.2302	$78.23	$78.25	$78.20
Purchase #5	$71.65	4.369%	$74.7804	$74.78	$74.80	$74.80
Purchase #6	$56.64	13.326%	$64.1878	$64.19	$64.20	$64.20
Purchase #7	$93.47	11.332%	$104.062	$104.06	$104.05	$104.10
7 purchase totals =	$680.44		$733.9559	$733.95	$734.00	$734.00