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	$60.36	7.792%	$65.0633	$65.06	$65.05	$65.10
Purchase #2	$19.92	6.750%	$21.2646	$21.26	$21.25	$21.30
Purchase #3	$150.57	9.104%	$164.2779	$164.28	$164.30	$164.30
Purchase #4	$134.62	5.576%	$142.1264	$142.13	$142.15	$142.10
Purchase #5	$94.91	9.639%	$104.0584	$104.06	$104.05	$104.10
Purchase #6	$241.30	7.147%	$258.5457	$258.55	$258.55	$258.50
Purchase #7	$89.54	7.294%	$96.071	$96.07	$96.05	$96.10
7 purchase totals =	$791.22		$851.4073	$851.41	$851.40	$851.50